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Allan Hills A81313
Basic information Name: Allan Hills A81313
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81313
This meteorite may also be called Allan Hills 81313 (ALH 81313) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 0.5 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 8(1)  (1985)  Shergottite (?)
AMN 13(3)  (1990)  Eucrite
AMN 17(1)  (1994)  Eucrite-pmict
Meteoritical Bulletin:  MB 76  (1994)  Eucrite-pmict
NHM Catalogue:  5th Edition  (2000)  Eucrite-pmict
MetBase:  v. 7.1  (2006)  Eucrite-pmict
Recommended:  Eucrite-pmict    [explanation]

This is 1 of 341 approved meteorites classified as Eucrite-pmict.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Writeuphelp
Writeup from AMN 8(1):

Sample No.: ALHA81313

Location: Allan Hills

Weight (g): 0.5

Field No.: 1680

Dimensions (cm): 0.8 x 0.7 x 0.4

Meteorite Type: Shergottite (?)

 

Macroscopic Description: Roberta Score

The stone is dark in color. The interior was not examined because this small specimen was not chipped and the entire mass was made into a thin section.

 

Thin Section (,1) Description: Brian Mason

The section shows a granular aggregate (grains 1-3 mm in maximum dimensions) of colorless plagioclase (maskelynite) and pale gray, weakly pleochroic pyroxene with trace amounts of opaque minerals (nickel-iron, troilite, chromite). A vague impression of pyroxene-rich and plagioclase-rich layers is present, possibly suggesting a cumulate. The pyroxene appears to be an inverted pigeonite with small blebs of exsolved augite. Point counting gives the following volume percentages: pyroxene, 54; plagioclase, 46. Microprobe analyses show the maskelynite is essentially stoichiometric and fairly uniform in composition, average An93 (Na2O 0.6-1.4%, K2O 0.04). Orthopyroxene composition is also fairly uniform, (average Ca 2.7 Fe 38; Al2O3 0.4%, MnO 0.9%, TiO2 0.2%, Cr2O3 0.3%). Composition of a single augite bleb is Ca38Fe20. In texture and mineral compositions this meteorite closely resembles the Moama monomict eucrite (Meteoritics, 10, p. 101, 1975). However, the presence of maskelynite indicates that ALHA81313 may be classed petrographically as a shergottite rather than a eucrite.

Data from:
  MB76
  Table 2
  Line 834:
Origin or pseudonym:Main icefield
Mass (g):0.5
Class:Eu "pm"
Ferrosilite (mol%):38
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 8(1) (1985), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (76° 43'S, 159° 40'E)
     Recommended::   (76° 41' 21"S, 159° 21' 51"E)
Note: the NHM and MetBase coordinates are 8.4 km apart

Statistics:
     This is 1 of 39173 approved meteorites from Antarctica (plus 5051 unapproved names)
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