[meteorite-list] The Perils of Type Collecting - A Guide

From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Wed, 3 Mar 2010 18:18:46 -0500
Message-ID: <e51421551003031518r72c69d49q5648e286ab9eba6d_at_mail.gmail.com>

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

-- 
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Mike Gilmer - Galactic Stone & Ironworks Meteorites
http://www.galactic-stone.com
http://www.facebook.com/galacticstone
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Received on Wed 03 Mar 2010 06:18:46 PM PST