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Allan Hills A81012
Basic information Name: Allan Hills A81012
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81012
This meteorite may also be called Allan Hills 81012 (ALH 81012) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 36.7 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 6(1)  (1983)  Eucrite
AMN 13(1)  (1990)  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 339 approved meteorites classified as Eucrite-pmict.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Writeuphelp
Writeup from AMN 6(1):

Sample No.: ALHA81012

Location: Allan Hills

Field No.: 1490

Weight (gms): 36.6

Meteorite Type: Eucrite

Physical Description: Roberta Score

Flow marks are present on the shiny black fusion crust which covers 75% of ALHA81012. Small clasts (<2 mm) are abundant in the light gray interior matrix. A few areas have oxidized to an orangish-brown color. Dimensions: 5 x 2 x 3 cm.

 

Petrographic Description: Brian Mason

The section consists largely of brown grains of pigeonite up to 0.9 mm and colorless grains of plagioclase up to 0.6 mm in a comminuted groundmass of these minerals. A few lithic clasts, up to 2.5 mm across, are present; most show ophitic textures. Fusion crust is present along one edge. Microprobe analyses show pyroxene compositions ranging fairly continuously from Wo3En35Fs62 to Wo35En32Fs33; En content shows a limited range (30-40) except for one grain Wo8En48Fs44. Plagioclase composition range is An84-94, mean An89. The meteorite is a eucrite, but it differs from previously described eucrites from the Allan Hills in the range and distribution of pyroxene compositions. It resembles ALHA81009 closely and is tentatively paired with that meteorite.

Data from:
  MB76
  Table 2
  Line 535:
Origin or pseudonym:Main icefield
Mass (g):36.7
Class:Eu "pm"
Weathering grade:A/B
Ferrosilite (mol%):33-62
Comments:76005 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 6(1) (1983), 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° 42' 19"S, 159° 18' 18"E)
Note: the NHM and MetBase coordinates are 9.4 km apart

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