[meteorite-list] The Perils of Type Collecting - A Guide
From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Thu, 4 Mar 2010 02:49:36 +0100 Message-ID: <003501cabb3c$f2657e10$07b22959_at_name86d88d87e2> Hi Mike, fine article. Maybe a remark :-) >The danger of type collecting (besides the damage to one's checking >account) There we can see, what the desert rush has opened for unbelievable opportunities to the collector! Just step 10 years back in time! There such a task, to accomplish a complete type collection, would have been almost impossible. There were only the Libyan finds (well and some types didn't exist yet) and the problem was, that one hadn't much choice. Often with the rarest types, you could choose only from one or two locales. And it was a costly thing. For an ACAP, which cost today 30$ a gram, you had to pay 1000-1500$/g. Something so extremely crazy like a Howardite (!!!!) cost 500$/g then, where you now often can win your little slice at 10$/g or so on ebay. >From lunaites, we better don't talk... Ureilites, Rumurutites... and so on. If something like that was available on a show, the collectors pressed their noses on the glass of the show cases, to catch a glimpse of such crazy material. Just 10 years ago. Now nearly everyone is able to set up a type collection, without selling the house, wife and children. Collectors, scientists, curators. That's also why it is so important, that the desert countries have to stay open for meteorite hunts. I noticed, that many collectors recognized, that they're living in the best period of meteorite history, and that they built up - aside their main focus (let it be the irons, or historic falls, or special types, or oriented ones or whatever) - a second, independent collection - a type collection! And let it be thumb-nail-sized slices, which still display often enough very typical characteristics for the classes. The elder collectors, because they suffered in these times, when such a task was unachievable, the younger ones, because they are curious and because they want to own all the variety of meteorites, they can find in the books and on the webpages - and because it's possible in NWA&Oman times, with a relatively modest budget. (Huh Mike, when I started, 30 years ago, you had the choice only between approx 300 meteorite locales, but also only with a lot of patience. Meteorites not types! Often it happened, that you found nothing new to buy and you took, for taking anything at all, an old weathered Texas H5 or L6 and you were happy about). How much has changed since! Best! Martin -----Urspr?ngliche Nachricht----- Von: meteorite-list-bounces at meteoritecentral.com [mailto:meteorite-list-bounces at meteoritecentral.com] Im Auftrag von Galactic Stone & Ironworks Gesendet: Donnerstag, 4. M?rz 2010 00:19 An: Meteorite List Betreff: [meteorite-list] The Perils of Type Collecting - A Guide Greetings Listees and fellow collectors, 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 this List 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 (Murchison) 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 C4 ungrouped C ungrouped (Tagish Lake, others) 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 -- ------------------------------------------------------------ Mike Gilmer - Galactic Stone & Ironworks Meteorites http://www.galactic-stone.com http://www.facebook.com/galacticstone ------------------------------------------------------------ ______________________________________________ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list at meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-listReceived on Wed 03 Mar 2010 08:49:36 PM PST |
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