To the veteran collector, there will be little of interest in this
post. This post is directed at the silent newbie or beginner lurkers
who are sorting through the web and trying to find their way around
the world of collecting meteorites.
Many new collectors often want one of each type of meteorite. Many
veteran collectors abandon this pursuit because the task is quite
daunting. So when you hear talk about "type collecting", or building
a "type collection", what exactly does that mean? I hope the
following brief article will answer those questions, or at least point
the reader in the right general direction. Note, I gleaned much of
this type information from David Weir's authoritative website
"Meteorite Studies" and from the Meteoritical Bulletin. I do not
claim that this list is 100% complete or without error, so if the
reader spots an error or omission, please reply and correct it.
-----
The Perils of Type Collecting ........
I started out collecting meteorites with a small sample of NWA 4293 -
an ordinary high iron chondrite of the H6 type. It was about the size
of a dog-food kibble and it looked like one. But I was instantly
hooked, and I wanted to have one each of the different types of
meteorite. This is known as "type collecting" or building a "type
collection".
The danger of type collecting (besides the damage to one's checking
account) is that the various petrologic types are subdivided into
various grades according to metamorphism.
For example, take the H chondrite group that my NWA 4293 sample belonged to.
There are H3 chondrites, H4 chondrites, H5 chondrites, and H6
chondrites. Did I really need one each of these subtypes? Well, it
depends on how deep a collector wants to go into the rabbit hole.
There are distinct differences between the various H types. The number
attached to each is more than just a simple weathering grade or shock
grade. It represents a progession in the H-chondrite family from least
altered to most altered. H3 chondrites are loaded with chondrules, H4
have some chondrules, H5 has few chondrules, and H6 has virtually no
visible chondrules. A new grade of H7 has been added as well. So, a
collector could simply have a single Hx chondrite and say that the
H-chondrites are represented. Or, the collector could have one each of
the different subtypes from 3 to 7.
Another peril is the changing of nomenclature. For example, the
K-subgroup of carbonaceous chondrites was only recognized and
designated in 1990. Up until then, Karoonda was considered a CV4
meteorite of the Vigarano family. Now Karoonda is recognized as
distinctly different type of carbonaceous chondrite, so it was made
into it's own group. Now we have CK4, CK5, and CK6 meteorites - all
represent a progression in metamorphism and have visible (and
chemical) differences from other grades. There are standout members of
each subgroup, so where does one draw the line? Should the collector
acquire a sample of Karoonda and be done with it? Or should the
collector go out and track down CK4, CK5 and CK6 meteorites? Again, it
depends on how extensive and exhaustive a collector wants to be with
their type collection. Budget will also play a role as well, because
an exhaustive type collection is a daunting project.
Lastly, one must consider the ungrouped meteorites. These are oddball
meteorites that do not neatly fit into the pre-existing meteorite
types. There are ungrouped chondrites, ungrouped achondrites, and
ungrouped irons. No type collection can overlook these meteorites
because some of them are types unto themselves with unique qualities.
For those who want to build a definitive and complete type collection,
here is a list of every known type and subtype of meteorite. This list
was culled from other sources, including David Weir's authoritative
"Meteorite Studies" website linked at the end of this post.
Carbonaceous Chondrites :
CI (Ivuna)
CM1 (Mighei)
CM2 (subdivided into CM2.0 to CM2.6)
CM3
CO3 (Ornans) (subdivided into CO3.03 to CO3.7)
CV (Vigarano) (also CV2 and CV3)
CK (Karoonda) (CK4, CK5, CK6)
CR (Renazzo) (CR1, CR2, CR3)
CB (Bencubbin)
CH
CR ungrouped
C2 ungrouped
C4 ungrouped
C ungrouped
Ordinary Chondrites :
Rumuruti R3 (subdivided into R3.5-6 to R3.9)
R4
R5
R6
LL (subdivided into LL3.0 to LL3.9)
LL4
LL5
LL5/6
LL6
LL6/7
LL7
LL impact melt
LL transitional (L/LL3 to L/LL6)
L (subdivided into L3.0 to L3.9)
L4
L5
L6
L6/7
L7
L impact melt
H/L transitional (H/L3 to H/L6 IMB, H/L3.6 to H/L3-4)
H (subdivided into H3.0 to H3.9)
H4
H5
H6
H7
H impact melt
ungrouped ordinary chondrites
Enstatite Chondrites :
EL (EL3 to EL7)
EL impact melt
EH/L
EH (EH3 to EH7)
EH impact melt
ungrouped enstatite chondrites
K (Kakangari)
Meta-chondrites (M-CV, M-CR, M-H, M-LL)
Primitive Chondrites :
Acapulcoite
Lodranite
Winonaites
ungrouped primitive chondrites
Achondrites :
Howardite (subdivided into fragmental breccia and regolith breccia)
Eucrite (monomict and polymict with each having subclasses)
Diogenite (monomict and polymict)
Olivine Diogenite
Dunite
Ureilite (monomict and polymict)
Martian achondrites :
Shergottite
Pyroxene-phyric basaltic shergottite
Olivine-phyric basaltic shergottite
Olivine-orthopyroxene-phyric basaltic shergottite
Pyroxene-peridotitic (Wehrlitic) shergottite
Lherzolitic shergottite
Diabasic shergottite
Nakhlite
Chassignite
Orthopyroxenite (ALH 84001)
Lunar Achondrites :
Feldspathic breccias
Regolith breccia
Fragmental breccia
Impact melt breccia
Granulitic breccia
Mafic-rich
Thorium-rich
KREEP-rich
Mingled Breccia
Mare Basalt
Other Achondrites :
Angrites (Plutonic and Basaltic)
Brachinite
Aubrite
ungrouped achondrites (Ibitira, Pasamonte, etc)
Stony-Irons :
Mesosiderites (1A,1B,2A,2B,2C,3A,3B,4A,4B)
ungrouped mesosiderites
Pallasites (Main Group, Eagle Station group, Pyroxene group)
Pallasite-am (anomalous, PMG-am, PMG-as)
ungrouped pallasites
Iron meteorites :
Note, iron meteorites are a can of worms. I will only focus on the
main chemical groups, and not the various grouplets and sub-types of
each main chemical group. Also note that many of these types include
silicated varities. Listing all of the known sub-types of irons would
require a LONG list resembling a flow-chart.
IAB
IC
IIAB
IIC
IID
IIE
IIF
IIG
IIIAB
IIIE
IIIF
IVA
IVB
ungrouped irons
I think that is all of them - as currently recognized by the Meteoritical Society Nomenclature Committee. If anyone can think of some I missed, please add them to this list.
David Weir's Meteorite Studies website - http://www.meteoritestudies.com/
Best regards and happy collecting!
MikeG
Galactic Stone Banner
Galactic Stone & Ironworks Meteorites
Monday, August 23, 2010
Lessons from the Saw - Tips and Advice for the Saw-Curious
I want to give a little background on my own cutting, so this will give some context to the tips and pointers I am going to offer below.
I use a Lortone Rock Rascal 6-inch lapidary saw. I paid about $300 for it. It is now discontinued by Lortone, but they are still available for purchase from some vendors as NOS - New Old Stock. It is the only rock saw I have personally used. I like this saw. I did some research before buying it and I considered several alternatives before deciding on this particular saw. I could have bought a bigger saw and budget was not a constraint - but I went with the 6-inch saw because I don't have much desire (or opportunity) to cut large specimens. The vast majority of the specimens I deal with are about the size of a golf ball (or smaller), so a 6-inch saw was all I needed.
I cut frequently and I have cut several types of material. I have cut some rocks, shells, and other non-meteorite materials, but I will limit my comments to cutting meteorites and tektites.
Materials I have cut - every type of OC one can imagine, highly weathered materials, fresh materials, carbonaceous chondrites (several types), mesosiderites, howardites, eucrites, and indochinites.
I don't cut irons. It's too labor intensive, time intensive, and it's hard on the equipment. So all of the advice below is geared towards cutting stony-type meteorites and some mesosiderites.
DISCLAIMER : I am not claiming to be an expert and these remarks are intended as unsolicited advice for newbies who are curious about cutting or would like to learn more about cutting. I do not claim that my methods and equipment are the best choice on the market. I use what I have and it works for me. Your mileage may vary.
SAW and CUTTING TIPS :
-------------------------------------
1) Bigger saws require bigger blades. Bigger saws make more noise and mess. Get a saw as big as you need - don't buy a saw that can cut a basketball-sized meteorite if you don't have access to such meteorites. Consider what you are going to need to cut and then decide what size saw to get. Keep in mind - half of the saw blade is under the table surface. So, a 6-inch saw has approx. 3 inches of useable cutting surface. This means the biggest meteorite you can properly cut in one pass on a 6-inch saw is about 3 inches in diameter. Replacement blades for larger saws are more expensive - another reason to get the proper size saw.
2) Avoid home improvement tile saws. I call these "Home Depot saws". Yes, they are cheap. And yes, they will cut meteorites. But, the blades are thick and are made for cutting materials like ceramic tile. Loss is not much of a consideration when cutting tiles for your shower surround. But, using that thick tile blade on a meteorite will result in a wide cutting swath of lost material and money. It's similar to swatting a fly with a baseball bat. If you want to lose half of every meteorite you cut, then buy a Home Depot saw. If you want a razor-thin cutting swath and minimal loss, get a true lapidary saw. Further proof of this is to take a look at any successful or experienced cutter - all of them use lapidary saws. (unless they cut irons, and then many use wire or band saws)
3) Don't use tap water as a coolant. Tap water contains chlorine, which will contaminate the material and result in an unstable specimen. Use distilled water only. Distilled water is cheap. You can buy it at Walmart for less than $1 a gallon. With a small 6" saw, a gallon goes a long way. It's well worth the investment. Your specimens will thank you and the people who end up owning those specimens will thank you.
4) A .012" kerf saw is plenty thin. Loss with a .012" blade is very minimal. There are thinner blades available, but some of them will not work with all saws. For example, there are ultra-thin blades that are .006" kerf. These blades are floppy and must be rotated at very high RPM's to maintain their rigidity during cutting. Always check your saw motor speeds and the size of your pulley before using one of these ultra-thin blades. I have tried both, and the .012" is plenty thin for me while still being rigid.
5) Everyone has their own ideas about what type of blade is best. I have tried the CBN blades (cubic boron nitride) that are supposedly designed for meteorites, and I didn't like them. I find that diamond blades cut much better than CBN blades. So, IMO, forget about CBN blades. I use the DiaLaser brand diamond-coated blades and they work very well for me. My next couple of blade purchases will be experimental and I am going to try a sintered Pro-Slicer blade. I will report back in the future about the performance of those blades.
6) You can dry cut a meteorite. I just don't recommend it for the majority of circumstances. If you have a very small and friable specimen that will not react well to getting wet, then you can dry cut. Keep in mind, dry cutting is hard on your blade and will result in a dull blade much faster than wet cutting. But, replacing a $30 blade might be a worthwhile trade off if you are cutting something fragile like Orgueil or something very valuable like a lunar or martian. 99% of the time, I cut wet.
7) Don't be in a hurry. Cutting meteorites is not a race. The faster you feed the specimen into the saw, the more likely the blade is to wander, resulting in a crooked or wedged cut. Feed slowly, consistently, and evenly. Cutting in a hurry will only result in poor cuts that require more work later to clean up. It's better not to leave a deep saw mark in the first place, than to spend time sanding it out later - which also results in more loss of material.
8) Don't be afraid to hand cut specimens. I've hand cut hundreds of specimens and have yet to cut my hand or fingers. (*knock on wood*) There are a wide variety of options of available for clamping specimens into a vise or jig that will hold the specimen during cutting. These result in nice straight even cuts. But, all of them have tradeoffs. First, some specimens are odd shaped or small, and they are difficult (or impossible) to clamp into a vise or jig. If you don't have a vise or jig, don't let that stop you from slicing. With practice, it is possible to make straight even cuts by hand. I own a sliding vise for slicing, but I rarely use it. I find it much easier to just hold the specimen in my own hands and I get better feedback during cutting because I can feel the specimen during the cut. I'm not saying that hand cutting is the best way to cut, I'm just saying that it works for me in many situations. Ultimately, the specimen itself may dictate what method is used to cut it.
9) If you do cut by hand - cut slowly and evenly. Do not feed to hard or quickly. Do not force the cut. Let the blade do the work and watch the cutting swath closely, especially in relation to the blade. A thin blade can flex in subtle ways that is not readily apparent, and this can result in an uneven cut. When the blade wanders in this manner, you will end up with slices that have a taper or wedged profile. Also, don't try to cut slices less than 1mm by hand, unless you can live with some breakage. Perhaps I am not experienced enough yet, but when I try to cut super thin slices by hand, it rarely works out well - that is where a feeding mechanism like a vise or jig comes in handy.
10) I guess I shouldn't have to say this, but for the record - wear safety goggles or safety glasses while cutting. Even if you wear eyeglasses, be sure to wear some impact-rated eyewear over those. You will save your eyesight and you will prevent your eyeglasses from being damaged.
11) If your saw doesn't have a light on it, get a "clamp lamp" or similar light fixture and set it up to illuminating the cutting area - with a focus on the blade zone. An adjustable desk lamp or shop lamp is good for this. If you want to safely make nice even cuts, you must be able to clearly see what you are cutting. Don't assume your garage that is sufficiently lit to cut plywood is bright enough to do detail cutting on small valuable meteorites - throw more light on the subject.
12) Keep a magnet handy. I have a magnet on the end of a pencil-sized wooden stick. I prop this up on the saw table during cutting and it helps prevent specimens from getting stuck to the blade or falling into the tank. It's also handy to collect crumbs and specks during cutting. If doing the latter, put a tiny ziploc bag over the end of the wand - to easily remove the crumbs later.
13) That little slot in the saw table that the blade passes through is too wide. Get a piece of thin, flat plastic and cut a small slit into it that will barely accomodate the cutting blade. Shape this piece of plastic to fit as a "template" that will drop onto the cutting table and can be removed easily. This will help prevent thin slices and pieces from dropping through the slot in the table and into the murky depths of the coolant tank. This little modification will pay for itself the first time is saves a thin slice of a rare fall from slipping into the tank.
14) Let the stone dictate where to cut. The shape, composition, and size of the stone will usually determine where to make the first cut. Carefully examine the stone prior to cutting and have a plan in mind - don't just start cutting willy nilly. Take notice of any fractures in the stone which may effect the cutting - if you cut across or along a fracture, the specimen will often crumble or a slice may break. Take into account the weathering state of the specimen as this may also effect the cutting.
15) Often you will have two choices for cutting a specimen - cutting it in a way which will expose the most surface area on the slices, or cutting it in a way that will produce the most slices. An example is an elongated or thin (or flat) specimen - if you cut it lengthwise along the narrow profile, you will yield pieces with the most surface area, but you will get fewer pieces. If you cut it widthwise across the longest dimension, you will get a loaf of bread type of affair - many pieces, but with less surface area on each. Which route is best is determined by a variety of factors that the cutter decides.
16) Have your oven on at 225-240F in advance of cutting. After cutting, take the specimens and put them directly into the oven without delay. Bake for 4-6 hours minimum, to purge any moisture from cutting. Some people like to chase the water out with alcohol prior to baking, but I have had good results without using alcohol and now I rarely use it.
17) After you are finished cutting, empty the coolant tank immediately, and then spin the blade dry. Keep your saw clean and tidy and don't let gunk build up between cuttings.
18) Saw marks are difficult to avoid and can be laborious to remove. As I said above, cut slowly and evenly and you will avoid deep saw marks. If you do get saw marks, keep some sandpaper handy in various grits from 100-600 - these grits are easiest to find at Wally World or home improvement stores. Start at 100 for deep saw marks on robust specimens, start at 200 or 220 if you have a more friable specimen. Place the sandpaper on a hard, level, flat surface and then place the specimen "face down" onto the sandpaper - press firmly and sand the specimen in a circular motion. Don't press too hard or the specimen may break or chip.
19) If you don't own a lap polisher, keep additional sandpaper handy in grits from 600 to 1500. Jeweler's rouge is also good to keep around - to achieve those hard glassy polishes.
20) If you aren't in the mood, don't cut. If you don't cherish your cutting time and love what you are doing, it will show in the results.
That's it for now. I am off to do some more cutting and polishing.
Best regards and happy cutting!
I use a Lortone Rock Rascal 6-inch lapidary saw. I paid about $300 for it. It is now discontinued by Lortone, but they are still available for purchase from some vendors as NOS - New Old Stock. It is the only rock saw I have personally used. I like this saw. I did some research before buying it and I considered several alternatives before deciding on this particular saw. I could have bought a bigger saw and budget was not a constraint - but I went with the 6-inch saw because I don't have much desire (or opportunity) to cut large specimens. The vast majority of the specimens I deal with are about the size of a golf ball (or smaller), so a 6-inch saw was all I needed.
I cut frequently and I have cut several types of material. I have cut some rocks, shells, and other non-meteorite materials, but I will limit my comments to cutting meteorites and tektites.
Materials I have cut - every type of OC one can imagine, highly weathered materials, fresh materials, carbonaceous chondrites (several types), mesosiderites, howardites, eucrites, and indochinites.
I don't cut irons. It's too labor intensive, time intensive, and it's hard on the equipment. So all of the advice below is geared towards cutting stony-type meteorites and some mesosiderites.
DISCLAIMER : I am not claiming to be an expert and these remarks are intended as unsolicited advice for newbies who are curious about cutting or would like to learn more about cutting. I do not claim that my methods and equipment are the best choice on the market. I use what I have and it works for me. Your mileage may vary.
SAW and CUTTING TIPS :
-------------------------------------
1) Bigger saws require bigger blades. Bigger saws make more noise and mess. Get a saw as big as you need - don't buy a saw that can cut a basketball-sized meteorite if you don't have access to such meteorites. Consider what you are going to need to cut and then decide what size saw to get. Keep in mind - half of the saw blade is under the table surface. So, a 6-inch saw has approx. 3 inches of useable cutting surface. This means the biggest meteorite you can properly cut in one pass on a 6-inch saw is about 3 inches in diameter. Replacement blades for larger saws are more expensive - another reason to get the proper size saw.
2) Avoid home improvement tile saws. I call these "Home Depot saws". Yes, they are cheap. And yes, they will cut meteorites. But, the blades are thick and are made for cutting materials like ceramic tile. Loss is not much of a consideration when cutting tiles for your shower surround. But, using that thick tile blade on a meteorite will result in a wide cutting swath of lost material and money. It's similar to swatting a fly with a baseball bat. If you want to lose half of every meteorite you cut, then buy a Home Depot saw. If you want a razor-thin cutting swath and minimal loss, get a true lapidary saw. Further proof of this is to take a look at any successful or experienced cutter - all of them use lapidary saws. (unless they cut irons, and then many use wire or band saws)
3) Don't use tap water as a coolant. Tap water contains chlorine, which will contaminate the material and result in an unstable specimen. Use distilled water only. Distilled water is cheap. You can buy it at Walmart for less than $1 a gallon. With a small 6" saw, a gallon goes a long way. It's well worth the investment. Your specimens will thank you and the people who end up owning those specimens will thank you.
4) A .012" kerf saw is plenty thin. Loss with a .012" blade is very minimal. There are thinner blades available, but some of them will not work with all saws. For example, there are ultra-thin blades that are .006" kerf. These blades are floppy and must be rotated at very high RPM's to maintain their rigidity during cutting. Always check your saw motor speeds and the size of your pulley before using one of these ultra-thin blades. I have tried both, and the .012" is plenty thin for me while still being rigid.
5) Everyone has their own ideas about what type of blade is best. I have tried the CBN blades (cubic boron nitride) that are supposedly designed for meteorites, and I didn't like them. I find that diamond blades cut much better than CBN blades. So, IMO, forget about CBN blades. I use the DiaLaser brand diamond-coated blades and they work very well for me. My next couple of blade purchases will be experimental and I am going to try a sintered Pro-Slicer blade. I will report back in the future about the performance of those blades.
6) You can dry cut a meteorite. I just don't recommend it for the majority of circumstances. If you have a very small and friable specimen that will not react well to getting wet, then you can dry cut. Keep in mind, dry cutting is hard on your blade and will result in a dull blade much faster than wet cutting. But, replacing a $30 blade might be a worthwhile trade off if you are cutting something fragile like Orgueil or something very valuable like a lunar or martian. 99% of the time, I cut wet.
7) Don't be in a hurry. Cutting meteorites is not a race. The faster you feed the specimen into the saw, the more likely the blade is to wander, resulting in a crooked or wedged cut. Feed slowly, consistently, and evenly. Cutting in a hurry will only result in poor cuts that require more work later to clean up. It's better not to leave a deep saw mark in the first place, than to spend time sanding it out later - which also results in more loss of material.
8) Don't be afraid to hand cut specimens. I've hand cut hundreds of specimens and have yet to cut my hand or fingers. (*knock on wood*) There are a wide variety of options of available for clamping specimens into a vise or jig that will hold the specimen during cutting. These result in nice straight even cuts. But, all of them have tradeoffs. First, some specimens are odd shaped or small, and they are difficult (or impossible) to clamp into a vise or jig. If you don't have a vise or jig, don't let that stop you from slicing. With practice, it is possible to make straight even cuts by hand. I own a sliding vise for slicing, but I rarely use it. I find it much easier to just hold the specimen in my own hands and I get better feedback during cutting because I can feel the specimen during the cut. I'm not saying that hand cutting is the best way to cut, I'm just saying that it works for me in many situations. Ultimately, the specimen itself may dictate what method is used to cut it.
9) If you do cut by hand - cut slowly and evenly. Do not feed to hard or quickly. Do not force the cut. Let the blade do the work and watch the cutting swath closely, especially in relation to the blade. A thin blade can flex in subtle ways that is not readily apparent, and this can result in an uneven cut. When the blade wanders in this manner, you will end up with slices that have a taper or wedged profile. Also, don't try to cut slices less than 1mm by hand, unless you can live with some breakage. Perhaps I am not experienced enough yet, but when I try to cut super thin slices by hand, it rarely works out well - that is where a feeding mechanism like a vise or jig comes in handy.
10) I guess I shouldn't have to say this, but for the record - wear safety goggles or safety glasses while cutting. Even if you wear eyeglasses, be sure to wear some impact-rated eyewear over those. You will save your eyesight and you will prevent your eyeglasses from being damaged.
11) If your saw doesn't have a light on it, get a "clamp lamp" or similar light fixture and set it up to illuminating the cutting area - with a focus on the blade zone. An adjustable desk lamp or shop lamp is good for this. If you want to safely make nice even cuts, you must be able to clearly see what you are cutting. Don't assume your garage that is sufficiently lit to cut plywood is bright enough to do detail cutting on small valuable meteorites - throw more light on the subject.
12) Keep a magnet handy. I have a magnet on the end of a pencil-sized wooden stick. I prop this up on the saw table during cutting and it helps prevent specimens from getting stuck to the blade or falling into the tank. It's also handy to collect crumbs and specks during cutting. If doing the latter, put a tiny ziploc bag over the end of the wand - to easily remove the crumbs later.
13) That little slot in the saw table that the blade passes through is too wide. Get a piece of thin, flat plastic and cut a small slit into it that will barely accomodate the cutting blade. Shape this piece of plastic to fit as a "template" that will drop onto the cutting table and can be removed easily. This will help prevent thin slices and pieces from dropping through the slot in the table and into the murky depths of the coolant tank. This little modification will pay for itself the first time is saves a thin slice of a rare fall from slipping into the tank.
14) Let the stone dictate where to cut. The shape, composition, and size of the stone will usually determine where to make the first cut. Carefully examine the stone prior to cutting and have a plan in mind - don't just start cutting willy nilly. Take notice of any fractures in the stone which may effect the cutting - if you cut across or along a fracture, the specimen will often crumble or a slice may break. Take into account the weathering state of the specimen as this may also effect the cutting.
15) Often you will have two choices for cutting a specimen - cutting it in a way which will expose the most surface area on the slices, or cutting it in a way that will produce the most slices. An example is an elongated or thin (or flat) specimen - if you cut it lengthwise along the narrow profile, you will yield pieces with the most surface area, but you will get fewer pieces. If you cut it widthwise across the longest dimension, you will get a loaf of bread type of affair - many pieces, but with less surface area on each. Which route is best is determined by a variety of factors that the cutter decides.
16) Have your oven on at 225-240F in advance of cutting. After cutting, take the specimens and put them directly into the oven without delay. Bake for 4-6 hours minimum, to purge any moisture from cutting. Some people like to chase the water out with alcohol prior to baking, but I have had good results without using alcohol and now I rarely use it.
17) After you are finished cutting, empty the coolant tank immediately, and then spin the blade dry. Keep your saw clean and tidy and don't let gunk build up between cuttings.
18) Saw marks are difficult to avoid and can be laborious to remove. As I said above, cut slowly and evenly and you will avoid deep saw marks. If you do get saw marks, keep some sandpaper handy in various grits from 100-600 - these grits are easiest to find at Wally World or home improvement stores. Start at 100 for deep saw marks on robust specimens, start at 200 or 220 if you have a more friable specimen. Place the sandpaper on a hard, level, flat surface and then place the specimen "face down" onto the sandpaper - press firmly and sand the specimen in a circular motion. Don't press too hard or the specimen may break or chip.
19) If you don't own a lap polisher, keep additional sandpaper handy in grits from 600 to 1500. Jeweler's rouge is also good to keep around - to achieve those hard glassy polishes.
20) If you aren't in the mood, don't cut. If you don't cherish your cutting time and love what you are doing, it will show in the results.
That's it for now. I am off to do some more cutting and polishing.
Best regards and happy cutting!
Sunday, August 22, 2010
Meteorites - Ambassadors from Space
"Meteorites - Ambassadors from Space" by Michael Gilmer.
Summary - this brief article explains what a meteorite is, where they come from, the major types of meteorites, and how to collect them.
It was by chance that I acquired my first meteorite. It was around Christmastime of 2006 and I was shopping for last-minute stocking stuffers for my wife and kids. Even though I am the only hardcore astronomy nut in the bunch, the rest of my immediate family has always been interested in space-related subjects. So, when I ran across an online ad for cheap meteorites, I took notice. These meteorites were hardly impressive to look at. They were tiny pebbles about the size of a dime, but they were priced just right at five bucks each. At first, I couldn't believe that one could own a meteorite so cheaply and easily. So using Google, I did a little homework on meteorites and the seller - to make sure the offer was legit. I soon discovered that although meteorites are considered quite rare, they are actually more available than most people think. The Earth is a large target whipping around the Sun in space, and it gets struck by meteorites at a constant and steady rate - like bugs hitting the windshield of a moving car. Most of these meteorites fall into the oceans which cover the bulk of the Earth's surface. Many others fall into inhospitable areas where they are unlikely to be found - jungles, mountaintops, forests, etc. However, a good number of meteorites land in areas where they are easily identified and collected - snowfields, deserts, dry lake beds, and plowed fields. In areas such as those, a strange looking rock tends to stand out like the proverbial sore thumb, and someone with the right knowledge can easily spot the meteorite and collect it. Not only do meteorites fall regularly (and get found regularly), but there are also dozens of types of meteorites with some more rare and interesting than others. Just like collecting conventional Earth-rocks, there is a thriving culture of hobbyists who collect and enjoy meteorites.
Collecting meteorites is related to the field of meteoritics (the study of meteorites), and it is a branch of planetary science that is not only accessible to the layman, but the layman is actually encouraged to participate. While I was waiting for my first meteorites to arrive in the mail, I did a lot of reading up on them and by the time the mailman finally brought my space rocks, I was excited like a kid in anticipation of Christmas morning. When the package arrived, I eagerly tore it open and saw a handful of small brown pebbles that resembled pieces of dog food. They were heavy for their small size, very smooth, and strongly attracted to a magnet due to their high metal content. But the most fascinating aspect of these unassuming little stones was their origin. In my hand, I was holding a rock from outer space that was as old as the Earth itself. These meteorites had formed out of the solar nebula around the same time that the planets had formed - over 4.5 billion years ago. Long before the first single-celled organisms had developed on an infant Earth, these stones had coalesced in the hard vacuum of space, and there they had circled our young sun as small members of our planetary family.
So, how did this chunk of space rock end up in my hand? At some point in the evolution of our solar system, a number of large asteroid-type bodies coexisted with our adolescent planets. Circling around the sun in a chaotic dance of creation, these bodies would cross each other's orbits and eventually some of them collided. These collisions were violent and they tore apart the parent bodies of the meteorites, smashing them to bits. These tiny bits (meteoroids) of debris continued on in their own orbits until a combination of fate and physics led them to cross paths with Earth. They were captured by Earth's gravity and pulled down through our atmosphere for a fiery descent. Many meteors will burn up completely in the violent passage through our dense atmosphere. But some were large enough and hardy enough to survive the trip and they landed on the ground intact.
Once a meteoroid enters the atmosphere, it becomes a meteor - that familiar shooting star streak of light that kids make wishes on and adult stargazers delight in seeing. And once that meteor hits the ground, it becomes a meteorite. This rain of falling meteorites has continued, unabated, for billions (and billions) of years. The deserts and snowfields of the world are literally peppered with meteorites that have fallen to Earth. Many oxidize away and are never found because the Earth is not a meteorite-friendly environment. In space, there is no oxygen, moisture, or wind, so the meteorites exist in a nearly-perfect state of "deep freeze" where they are protected from the effects of weathering. Once the meteorites are exposed to Earth's air, wind and water, they begin to break down. Stony-type meteorites will simply weather away into their base components and will eventually lose their identity as meteorites. Iron-type meteorites will likewise rot into a pile of rusty iron shale fragments. If the meteorites are not collected and preserved, they are simply lost forever.
Any article that would attempt to explain all the various types of meteorites, how they were formed, and what they are made up of, would entail far more space than I have here. Indeed, entire libraries of books have been written on the subject, and much is still unknown or under debate about meteorites. Here I will attempt to briefly detail the major types of meteorites and what makes them interesting to science and the layman collector.
There are 3 main types of meteorites - stony, iron, and stony-iron. Stony meteorites are exactly what they sound like; they are rocky combinations of minerals that could be easily mistaken for an Earth rock if not for their peculiar properties.
Iron meteorites are pieces of solid metal that are very dense and contain high concentrations of the element nickel. Imagine something as dense as a piece of a railroad track and you get some idea how heavy iron meteorites are for their size.
Stony-irons are a combination of the two types - part stone and part iron, mixed together into a single mass.
While stony meteorites are more common, iron meteorites are more resilient, tend to resist weathering, and survive impact more often than some stony types. In addition to these 3 major types of meteorites, there are many sub-types and variations which would fill up an encyclopedia (see Richard Norton’s Encyclopedia of Meteorites for a complete treatment of all types). Some of the most interesting of the rare types are the so-called "planetary" meteorites. Planetary meteorites have been determined to originate from large familiar parent bodies, like the Moon and Mars. Yes, you read correctly - some meteorites are actually fragments of our Moon and the planet Mars! How is it possible that a piece of the Moon or Mars ended up on Earth? In fact, most of the craters you can observe on the Moon were caused by meteorite impacts! A long time ago, a large meteorite that was a mile across (or bigger) slammed into the surface of the Moon or Mars. The resulting catastrophic impact and explosion hurled large amounts of material upwards which escaped the feeble gravity of these planets and escaped into space. These fragments then floated around in the solar system until they crossed paths with Earth's orbit and were captured by our gravity. In this manner, small pieces of other worlds can actually land on Earth! These planetary meteorites are the rarest of the rare and are highly desired by collectors and scientists alike for what they can teach us about the evolution of planets, including our own.
Now I would like to address the obvious question - how do we really know it's a meteorite? I get that question all the time, mostly from people who are curious about meteorites, but have no prior experience with them. This is a relatively easy question to answer because meteorites possess some peculiar properties that are not present in Earth materials. First and foremost is the content of elemental nickel. Pure nickel is exceedingly rare in the Earth's crust and the vast majority of the Earth's nickel is found deep down in the core of our planet. The nickel that is present on the surface of the Earth (or near the surface) is contained in combined ores and not in a pure elemental form. Pure nickel must be extensively processed out of the raw ore, and one just doesn't find Earth rocks or minerals with pure nickel in them. Any "rock" that has high nickel content is automatically a meteorite suspect. One can easily determine a sample's nickel content by doing a simple chemical reaction test. Another hallmark of meteorites are "chondrules" - which are small spheres of various minerals which are embedded in the body (or matrix) of the meteorite. These chondrules are distinctive and unlike any Earthly formation of minerals. On a sliced meteorite, chondrules will appear as little circles embedded in the rocky matrix. This is the result of the saw cutting through the spherical chondrules - revealing them in cross section. Chondrules are the product of processes that are not present on Earth, so if one has a rock with chondrules in it, then it's a meteorite. There are other litmus tests as well, including specific gravity, and the degree of magnetic attraction.
As recently as the 1950’s, the exact origin and nature of meteorites was under hot debate, but after decades of scientific study, meteorites are now well-understood and can be easily distinguished from earthly materials. But how do we know a Martian meteorite is really from Mars or that a lunar meteorite is really from the Moon? The answer is again found in chemical and physical analysis. Thanks to the astronauts of the Apollo program, we have actual Moon rocks that were brought back from the surface of the Moon. Comparing these known Moon rocks against suspected lunar meteorites allows us to determine not only that a meteorite came from the Moon, but we can also determine if the meteorite came from the low-lying lunar basins or the mountains of the lunar highlands - because each have their own chemical and physical signatures. In the case of Martian meteorites, we can compare their chemistries against the known chemistries of Martian materials that we have analyzed with remote Martian rovers like Sojourner. There is now no doubt such meteorites are truly pieces of other worlds.
Now that we have established what meteorites are and how we determine their origins, let's examine how the meteorite finds its way onto the open marketplace. Most of the meteorites on the collector market come from the deserts of North West Africa. These meteorites are called "NWA" meteorites and the bulk of them come from the Saharan desert. Any rock lying out in the middle of the open desert by itself is automatically suspect. In areas such as the Saharan, where native rock is either absent or highly distinctive, a curious looking rock that is out of place must have fallen from the sky. In some cases, the meteorite is actually seen to fall to Earth by eyewitnesses - these meteorites are called "witnessed falls". Conversely, when someone stumbles across a meteorite, recognizes it as unusual and picks it up, that is called a “find”. This is mostly done by Bedouin nomads and other desert dwellers that are intimately familiar with the sand dunes and know something special when they see it. They collect these stones from the open desert and bring them back to marketplaces in Morocco or large rock shows like the one in Tucson every year. In these marketplaces, Western collectors and dealers comb through the offerings and purchase promising specimens to bring back to the states or Europe. Sometimes these meteorites are relatively-common types and they are sold as unclassified NWA meteorites (UNWA) - this means they have been identified as meteorites due to their properties, but they have not been formally analyzed by a laboratory. If a particular meteorite seems promising as a potentially rare type (like a Lunar or Martian), then a piece of it is sent off to a respected laboratory for analysis. This analysis is intensive and can takes months of study, which includes thin-sectioning and study with scanning electron microscopes and other instruments to determine its exact chemical composition. Once analyzed, the meteorite can be compared to other known meteorites and then it is officially "classified". A classified meteorite is given a name and/or number in the official catalogue of the Meteoritical Society. Classified meteorites typically have names like "Bassikounou" which means that particular meteorite was found near Bassikounou Mauritania. Meteorites, whose exact places of discovery are known, are given place names such as the nearest post office or permanent landmark. Meteorites whose exact point of discovery cannot be determined (because they were moved and then sold at a marketplace) are given catalogue numbers like NWA 869. Generally speaking, since meteorites which are seen to fall (witnessed falls) are rarer than found meteorites (finds), witnessed falls are more valuable to the collector.
At some point, the meteorite is offered for sale on the marketplace by the owner, finder, or dealer. Of course, the internet is a great boon to collectors and there are a wide variety of meteorites available from dealer websites, eBay, and collector groups. There are some frauds (like most hobbies that involve valuable collectibles) and there will always be someone trying to pass off a fake or misrepresented meteorite. Since meteorites are rarer than diamonds or gold, one must be a savvy buyer to avoid possible scams. The best way to ensure that a meteorite being offered for sale is the real thing is to check the credentials of the seller. Credentials to look for include membership in the Meteoritical Society and the IMCA (International Meteorite Collectors Association). The IMCA is group of collectors and dealers who maintain a code of standards and ethics for selling or trading meteorites. The Meteoritical Society is the official governing body of meteorite study and it is comprised of scientists, collectors and dealers. It is the Meteoritical Society that publishes the official classifications of all meteorites. Both of these organizations are generally a safe bet to buy legitimate meteorites from members. If purchasing from a marketplace like eBay, use a good measure of common sense and examine the seller's feedback ratings. Prices for meteorites on the open market can vary widely from dealer to dealer. Unlike gold or diamonds which have a regulated market with going rates, the price of meteorites is dictated solely by supply and demand. One dealer may charge $20 for a given meteorite and another dealer may be selling an identical meteorite for $100, so it pays to shop around and compare prices. Assuming one has purchased a meteorite, what does one do with it?
Meteorites are fascinating for what they can teach us about the solar system because they are 4+ billion year old ambassadors of outer space. It's a thrill to hold something older than the Earth in our hands. Meteorites can be displayed, stored, and shared like any other valuable collectible. What's more, meteorites make great outreach props for astronomy. Children absolutely love meteorites! Give a child a meteorite to hold and tell him/her it's a piece of a shooting star and watch his/her eyes light up with wonder and delight! And at this point, I think I should warn our readers that collecting meteorites is much like eating potato chips - you can't have just one. It's a very addictive hobby that meshes well with astronomy, telescopes and stargazing. After all, one can look at the planets through a telescope, and then actually hold a piece of one!
Meteorites should be cared for like any other rare collectible - they should be handled with care and properly maintained. This means keeping them away from moisture and sources of oxidation which might damage or degrade the meteorite. After handling a meteorite, it should be wiped clean with a dry cloth and stored in a dry area. A Tupperware container with a packet of desiccant to absorb moisture is an ideal way to store meteorites. With proper care, a meteorite will last for many generations to come.
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So, do you want to learn more about meteorites and how to collect them? I strongly recommend two books and one magazine for those who want to do their homework on meteorites. The first is Rocks from Space by O. Richard Norton. This is the definitive book in the field of meteorites and it covers every fundamental aspect of meteorites and collecting. It is understandable to the layman and is not laden with dense math and complex terminology. The second book is Cosmic Debris by John G. Burke. This is a more serious work for the advanced enthusiast and it covers the history of meteoritics from its very beginnings hundreds of years ago to the latest theories today. Cosmic Debris also includes a fascinating chapter on the folklore of meteorites and describes how meteorites were viewed by primitive people, including the legends that surrounded these objects hurled from space. Unfortunately, Cosmic Debris is no longer in print, but used copies can be found from online book dealers. Last but not least, there is Meteorite Magazine, which is the only periodical dedicated solely to meteorites and their study. It is a quarterly publication of the Arkansas Center for Space and Planetary Sciences and it is loaded with informative articles and beautiful photos. The interested reader will find that meteorites are much like astronomy in general - the people who are interested in these fields are very friendly and approachable folks who love to share their knowledge about space. If after reading this, you still have questions about meteorites, feel free to contact me via email and I will do my best to answer them for you. :)
(c) Copyright 2008, Michael W. Gilmer
Summary - this brief article explains what a meteorite is, where they come from, the major types of meteorites, and how to collect them.
It was by chance that I acquired my first meteorite. It was around Christmastime of 2006 and I was shopping for last-minute stocking stuffers for my wife and kids. Even though I am the only hardcore astronomy nut in the bunch, the rest of my immediate family has always been interested in space-related subjects. So, when I ran across an online ad for cheap meteorites, I took notice. These meteorites were hardly impressive to look at. They were tiny pebbles about the size of a dime, but they were priced just right at five bucks each. At first, I couldn't believe that one could own a meteorite so cheaply and easily. So using Google, I did a little homework on meteorites and the seller - to make sure the offer was legit. I soon discovered that although meteorites are considered quite rare, they are actually more available than most people think. The Earth is a large target whipping around the Sun in space, and it gets struck by meteorites at a constant and steady rate - like bugs hitting the windshield of a moving car. Most of these meteorites fall into the oceans which cover the bulk of the Earth's surface. Many others fall into inhospitable areas where they are unlikely to be found - jungles, mountaintops, forests, etc. However, a good number of meteorites land in areas where they are easily identified and collected - snowfields, deserts, dry lake beds, and plowed fields. In areas such as those, a strange looking rock tends to stand out like the proverbial sore thumb, and someone with the right knowledge can easily spot the meteorite and collect it. Not only do meteorites fall regularly (and get found regularly), but there are also dozens of types of meteorites with some more rare and interesting than others. Just like collecting conventional Earth-rocks, there is a thriving culture of hobbyists who collect and enjoy meteorites.
Collecting meteorites is related to the field of meteoritics (the study of meteorites), and it is a branch of planetary science that is not only accessible to the layman, but the layman is actually encouraged to participate. While I was waiting for my first meteorites to arrive in the mail, I did a lot of reading up on them and by the time the mailman finally brought my space rocks, I was excited like a kid in anticipation of Christmas morning. When the package arrived, I eagerly tore it open and saw a handful of small brown pebbles that resembled pieces of dog food. They were heavy for their small size, very smooth, and strongly attracted to a magnet due to their high metal content. But the most fascinating aspect of these unassuming little stones was their origin. In my hand, I was holding a rock from outer space that was as old as the Earth itself. These meteorites had formed out of the solar nebula around the same time that the planets had formed - over 4.5 billion years ago. Long before the first single-celled organisms had developed on an infant Earth, these stones had coalesced in the hard vacuum of space, and there they had circled our young sun as small members of our planetary family.
So, how did this chunk of space rock end up in my hand? At some point in the evolution of our solar system, a number of large asteroid-type bodies coexisted with our adolescent planets. Circling around the sun in a chaotic dance of creation, these bodies would cross each other's orbits and eventually some of them collided. These collisions were violent and they tore apart the parent bodies of the meteorites, smashing them to bits. These tiny bits (meteoroids) of debris continued on in their own orbits until a combination of fate and physics led them to cross paths with Earth. They were captured by Earth's gravity and pulled down through our atmosphere for a fiery descent. Many meteors will burn up completely in the violent passage through our dense atmosphere. But some were large enough and hardy enough to survive the trip and they landed on the ground intact.
Once a meteoroid enters the atmosphere, it becomes a meteor - that familiar shooting star streak of light that kids make wishes on and adult stargazers delight in seeing. And once that meteor hits the ground, it becomes a meteorite. This rain of falling meteorites has continued, unabated, for billions (and billions) of years. The deserts and snowfields of the world are literally peppered with meteorites that have fallen to Earth. Many oxidize away and are never found because the Earth is not a meteorite-friendly environment. In space, there is no oxygen, moisture, or wind, so the meteorites exist in a nearly-perfect state of "deep freeze" where they are protected from the effects of weathering. Once the meteorites are exposed to Earth's air, wind and water, they begin to break down. Stony-type meteorites will simply weather away into their base components and will eventually lose their identity as meteorites. Iron-type meteorites will likewise rot into a pile of rusty iron shale fragments. If the meteorites are not collected and preserved, they are simply lost forever.
Any article that would attempt to explain all the various types of meteorites, how they were formed, and what they are made up of, would entail far more space than I have here. Indeed, entire libraries of books have been written on the subject, and much is still unknown or under debate about meteorites. Here I will attempt to briefly detail the major types of meteorites and what makes them interesting to science and the layman collector.
There are 3 main types of meteorites - stony, iron, and stony-iron. Stony meteorites are exactly what they sound like; they are rocky combinations of minerals that could be easily mistaken for an Earth rock if not for their peculiar properties.
Iron meteorites are pieces of solid metal that are very dense and contain high concentrations of the element nickel. Imagine something as dense as a piece of a railroad track and you get some idea how heavy iron meteorites are for their size.
Stony-irons are a combination of the two types - part stone and part iron, mixed together into a single mass.
While stony meteorites are more common, iron meteorites are more resilient, tend to resist weathering, and survive impact more often than some stony types. In addition to these 3 major types of meteorites, there are many sub-types and variations which would fill up an encyclopedia (see Richard Norton’s Encyclopedia of Meteorites for a complete treatment of all types). Some of the most interesting of the rare types are the so-called "planetary" meteorites. Planetary meteorites have been determined to originate from large familiar parent bodies, like the Moon and Mars. Yes, you read correctly - some meteorites are actually fragments of our Moon and the planet Mars! How is it possible that a piece of the Moon or Mars ended up on Earth? In fact, most of the craters you can observe on the Moon were caused by meteorite impacts! A long time ago, a large meteorite that was a mile across (or bigger) slammed into the surface of the Moon or Mars. The resulting catastrophic impact and explosion hurled large amounts of material upwards which escaped the feeble gravity of these planets and escaped into space. These fragments then floated around in the solar system until they crossed paths with Earth's orbit and were captured by our gravity. In this manner, small pieces of other worlds can actually land on Earth! These planetary meteorites are the rarest of the rare and are highly desired by collectors and scientists alike for what they can teach us about the evolution of planets, including our own.
Now I would like to address the obvious question - how do we really know it's a meteorite? I get that question all the time, mostly from people who are curious about meteorites, but have no prior experience with them. This is a relatively easy question to answer because meteorites possess some peculiar properties that are not present in Earth materials. First and foremost is the content of elemental nickel. Pure nickel is exceedingly rare in the Earth's crust and the vast majority of the Earth's nickel is found deep down in the core of our planet. The nickel that is present on the surface of the Earth (or near the surface) is contained in combined ores and not in a pure elemental form. Pure nickel must be extensively processed out of the raw ore, and one just doesn't find Earth rocks or minerals with pure nickel in them. Any "rock" that has high nickel content is automatically a meteorite suspect. One can easily determine a sample's nickel content by doing a simple chemical reaction test. Another hallmark of meteorites are "chondrules" - which are small spheres of various minerals which are embedded in the body (or matrix) of the meteorite. These chondrules are distinctive and unlike any Earthly formation of minerals. On a sliced meteorite, chondrules will appear as little circles embedded in the rocky matrix. This is the result of the saw cutting through the spherical chondrules - revealing them in cross section. Chondrules are the product of processes that are not present on Earth, so if one has a rock with chondrules in it, then it's a meteorite. There are other litmus tests as well, including specific gravity, and the degree of magnetic attraction.
As recently as the 1950’s, the exact origin and nature of meteorites was under hot debate, but after decades of scientific study, meteorites are now well-understood and can be easily distinguished from earthly materials. But how do we know a Martian meteorite is really from Mars or that a lunar meteorite is really from the Moon? The answer is again found in chemical and physical analysis. Thanks to the astronauts of the Apollo program, we have actual Moon rocks that were brought back from the surface of the Moon. Comparing these known Moon rocks against suspected lunar meteorites allows us to determine not only that a meteorite came from the Moon, but we can also determine if the meteorite came from the low-lying lunar basins or the mountains of the lunar highlands - because each have their own chemical and physical signatures. In the case of Martian meteorites, we can compare their chemistries against the known chemistries of Martian materials that we have analyzed with remote Martian rovers like Sojourner. There is now no doubt such meteorites are truly pieces of other worlds.
Now that we have established what meteorites are and how we determine their origins, let's examine how the meteorite finds its way onto the open marketplace. Most of the meteorites on the collector market come from the deserts of North West Africa. These meteorites are called "NWA" meteorites and the bulk of them come from the Saharan desert. Any rock lying out in the middle of the open desert by itself is automatically suspect. In areas such as the Saharan, where native rock is either absent or highly distinctive, a curious looking rock that is out of place must have fallen from the sky. In some cases, the meteorite is actually seen to fall to Earth by eyewitnesses - these meteorites are called "witnessed falls". Conversely, when someone stumbles across a meteorite, recognizes it as unusual and picks it up, that is called a “find”. This is mostly done by Bedouin nomads and other desert dwellers that are intimately familiar with the sand dunes and know something special when they see it. They collect these stones from the open desert and bring them back to marketplaces in Morocco or large rock shows like the one in Tucson every year. In these marketplaces, Western collectors and dealers comb through the offerings and purchase promising specimens to bring back to the states or Europe. Sometimes these meteorites are relatively-common types and they are sold as unclassified NWA meteorites (UNWA) - this means they have been identified as meteorites due to their properties, but they have not been formally analyzed by a laboratory. If a particular meteorite seems promising as a potentially rare type (like a Lunar or Martian), then a piece of it is sent off to a respected laboratory for analysis. This analysis is intensive and can takes months of study, which includes thin-sectioning and study with scanning electron microscopes and other instruments to determine its exact chemical composition. Once analyzed, the meteorite can be compared to other known meteorites and then it is officially "classified". A classified meteorite is given a name and/or number in the official catalogue of the Meteoritical Society. Classified meteorites typically have names like "Bassikounou" which means that particular meteorite was found near Bassikounou Mauritania. Meteorites, whose exact places of discovery are known, are given place names such as the nearest post office or permanent landmark. Meteorites whose exact point of discovery cannot be determined (because they were moved and then sold at a marketplace) are given catalogue numbers like NWA 869. Generally speaking, since meteorites which are seen to fall (witnessed falls) are rarer than found meteorites (finds), witnessed falls are more valuable to the collector.
At some point, the meteorite is offered for sale on the marketplace by the owner, finder, or dealer. Of course, the internet is a great boon to collectors and there are a wide variety of meteorites available from dealer websites, eBay, and collector groups. There are some frauds (like most hobbies that involve valuable collectibles) and there will always be someone trying to pass off a fake or misrepresented meteorite. Since meteorites are rarer than diamonds or gold, one must be a savvy buyer to avoid possible scams. The best way to ensure that a meteorite being offered for sale is the real thing is to check the credentials of the seller. Credentials to look for include membership in the Meteoritical Society and the IMCA (International Meteorite Collectors Association). The IMCA is group of collectors and dealers who maintain a code of standards and ethics for selling or trading meteorites. The Meteoritical Society is the official governing body of meteorite study and it is comprised of scientists, collectors and dealers. It is the Meteoritical Society that publishes the official classifications of all meteorites. Both of these organizations are generally a safe bet to buy legitimate meteorites from members. If purchasing from a marketplace like eBay, use a good measure of common sense and examine the seller's feedback ratings. Prices for meteorites on the open market can vary widely from dealer to dealer. Unlike gold or diamonds which have a regulated market with going rates, the price of meteorites is dictated solely by supply and demand. One dealer may charge $20 for a given meteorite and another dealer may be selling an identical meteorite for $100, so it pays to shop around and compare prices. Assuming one has purchased a meteorite, what does one do with it?
Meteorites are fascinating for what they can teach us about the solar system because they are 4+ billion year old ambassadors of outer space. It's a thrill to hold something older than the Earth in our hands. Meteorites can be displayed, stored, and shared like any other valuable collectible. What's more, meteorites make great outreach props for astronomy. Children absolutely love meteorites! Give a child a meteorite to hold and tell him/her it's a piece of a shooting star and watch his/her eyes light up with wonder and delight! And at this point, I think I should warn our readers that collecting meteorites is much like eating potato chips - you can't have just one. It's a very addictive hobby that meshes well with astronomy, telescopes and stargazing. After all, one can look at the planets through a telescope, and then actually hold a piece of one!
Meteorites should be cared for like any other rare collectible - they should be handled with care and properly maintained. This means keeping them away from moisture and sources of oxidation which might damage or degrade the meteorite. After handling a meteorite, it should be wiped clean with a dry cloth and stored in a dry area. A Tupperware container with a packet of desiccant to absorb moisture is an ideal way to store meteorites. With proper care, a meteorite will last for many generations to come.
So, do you want to learn more about meteorites and how to collect them? I strongly recommend two books and one magazine for those who want to do their homework on meteorites. The first is Rocks from Space by O. Richard Norton. This is the definitive book in the field of meteorites and it covers every fundamental aspect of meteorites and collecting. It is understandable to the layman and is not laden with dense math and complex terminology. The second book is Cosmic Debris by John G. Burke. This is a more serious work for the advanced enthusiast and it covers the history of meteoritics from its very beginnings hundreds of years ago to the latest theories today. Cosmic Debris also includes a fascinating chapter on the folklore of meteorites and describes how meteorites were viewed by primitive people, including the legends that surrounded these objects hurled from space. Unfortunately, Cosmic Debris is no longer in print, but used copies can be found from online book dealers. Last but not least, there is Meteorite Magazine, which is the only periodical dedicated solely to meteorites and their study. It is a quarterly publication of the Arkansas Center for Space and Planetary Sciences and it is loaded with informative articles and beautiful photos. The interested reader will find that meteorites are much like astronomy in general - the people who are interested in these fields are very friendly and approachable folks who love to share their knowledge about space. If after reading this, you still have questions about meteorites, feel free to contact me via email and I will do my best to answer them for you. :)
(c) Copyright 2008, Michael W. Gilmer
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