Meteorite**NWA 4931, Angrite**5.089 grams, Very Rare & Unique Angrite!!!

Description

Hello up for sale is NWA 4931 classified as a very rare and unique Angrite paired to NWA 2999. This slice weighs 5.089 grams, with a perfect mirror polish to one side and nice shape. Grain size is predominantly from 0.1 to 0.5 mm, but all stones have irregularly distributed, larger yellowish plagioclase grains (up to 6 mm across) exhibiting an iridescent luster. This meteorite is very rare and comes from an Angrite Parent Body! This meteorite comes with 2 COA cards Streaming Meteorites and Mark Lyon and display case. Thanks for your interest and take care.
This is an OFFICIAL meteorite name.
Abbreviation: NWA 4931
Observed fall: No
Year found: 2007
Country: (Northwest Africa)
Mass: 2.14 kg
This is 1 of 38 approved meteorites classified as Angrite.
Physical Characteristics: Grain size is predominantly from 0.1 to 0.5 mm, but all stones have irregularly distributed, larger yellowish plagioclase grains (up to 6 mm across) exhibiting an iridescent luster.
Petrography: (A. Irving and S. Kuehner, UWS; T. Bunch and J. Wittke, NAU) Based upon examination of thin sections of all separate stones, this meteorite is texturally heterogeneous. Terrestrial weathering has resulted in partial replacement of metal and minor grain boundary staining by iron hydroxides. The overall texture is protogranular, but there are large porphyroclasts of anorthite, spinel, and polygranular olivine. Anorthite also occurs as narrow (10–20 µm wide) coronas around spinel grains adjacent to clinopyroxene and both spinel and diopside are compositionally zoned away from the coronas. Texturally, this meteorite is very different from most angrites.
Geochemistry: The major minerals are Ca-rich olivine (Fa39.8–41.0; FeO/MnO = 77–97; CaO = 0.6–1.3 wt%), Al,Ti-bearing diopside (Fs9.6–11.3Wo53–54; FeO/MnO = 55–130; Al2O3 = 5–9, TiO2 = 0.5–2.4 [both wt%]), minor Cr-pleonaste spinel (Mg/(Mg+Fe) = 0.44–0.47, Al2O3 = 55–60, Cr2O3 = 4.7–8.7 [both wt%]), pure anorthite (containing Na2O < 0.02 wt%), and kamacite, troilite, and S-bearing calcium silicophosphate. Oxygen isotopes: (D. Rumble, CIW) Triplicate analyses of acid-washed whole rock samples by laser fluorination gave, respectively, δ18O = 3.839, 4.093, 4.154; δ17O = 1.974, 2.054, 2.095; ∆17O = −0.041, −0.095, −0.086 (all ‰).
Classification: Achondrite (angrite).
Search for other: Achondrites, Angrites
Comments:Approved 4 May 2008
Data from:
MB94
Table 2
Line 87:
State/Prov/County:Tagounite
Date:Oct-2007
Mass (g):2140
Pieces:2
Class:Angrite
Fayalite (mol%):39.3-39.5
Ferrosilite (mol%):10.1-10.4
Wollastonite (mol%):53.9-52.3
Classifier:A. Irving and S. Kuehner, UWS
Type spec mass (g):28.2
Type spec location:UWS
Main mass:GHupé
Comments:Paired with NWA 2999
Institutions
and collectionsUWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012)
GHupé: Gregory M. Hupé, 9003 Placid Lakes Blvd., Lake Placid, FL 33852, United States; Website (private address)
Northwest Africa 4931 (or, NWA 4931) is the 3rd most massive Angrite stone. However, it is part of the NWA 2999 pairing group of 7 meteorites with a total mass of ~6 kg. Pieces of a single meteoroid are, of course, frequently separated during atmospheric entry and/or upon impact with the earth’s surface. In the meteoritical literature, the pieces are then referred to as pieces of a single meteorite. With most NWA meteorites, however, it is often impossible to separate many natural effects from subsequent human activities — specimen divisions to increase profits and various efforts to keep the location site(s) secret. It is highly likely, then, that NWA 4931 is simply the largest piece of a single meteorite. We list here only those mineral species which have been found in the NWA 4931 ‘fragment.’ Presumably, a listing under NWA 2999 (The first fragment to be found) would be the appropriate site for a complete inventory of the meteorite sensu strictu.
References to NWA 4931 are scarce and many electronic publications are available to the public only in abstract form. Angrites are invariably characterized by the presence of Fassaite (Ti-rich Augite) and Ca-rich Olivine. Plagioclase and Kirschsteinite are usually present as well. The Goethite and Magnetite listed here were reported as weathering products. However, one should note that Ti-rich Magnetite is reported in other Angrites as normal members of the characteristic Al,Ca,Ti-rich assemblages which distinguish Angrites from other igneous achondrites.