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Allan Hills A81011
Basic information Name: Allan Hills A81011
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81011
This meteorite may also be called Allan Hills 81011 (ALH 81011) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 406 g
Antarctic Meteorite Newsletter:  AMN 6(1)  (1983)  Eucrite-br
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 391 approved meteorites classified as Eucrite-pmict.   [show all]
Search for other: Achondrites, Eucrites, and HED achondrites
Writeup from AMN 6(1):

Sample No.: ALHA81011

Location: Allan Hills

Field No.: 1435

Weight (gms): 405.7

Meteorite Type: Eucritic Breccia (possibly a genomict breccia)


Physical Description: Roberta Score

Rounded with scattered patches of black fusion crust, this breccia is clast; rich. Several types of clasts are present-typical eucritic clasts, pinkish-white clasts and massive gray clasts. These clasts range in shape from rounded, to lens-shaped, to rectangular, and many are larger than 1.5 cm long. The exterior matrix has a light gray color while the fresh interior matrix is very fine-grained and black. Several areas of oxidation are visible. Dimensions: 8 x 6 x 5 cm.


Petrographic Description: Brian Mason

The meteorite is a breccia of eucritic clasts up to 10 mm in maximum dimension, the clasts sitting in a minor amount of dark glass filled with comminuted grains of pyroxene and plagioclase. The clasts consist of pyroxene and plagioclase and show a variety of textures--finely granular, subophitic, and gabbroic. Microprobe analyses show pyroxene compositions corresponding to pigeonite and augite and clustering around two mean compositions, WoEn36Fs60 and Wo35En32Fs33, with a few intermediate values. Plagioclase has fairly uniform composition, An87-91, mean An88. The meteorite is a eucritic breccia; although it appears to be polymict, the uniformity of mineral compositions suggest a considerable degree of equilibration, and it may be a genomict breccia.

Data from:
  Table 2
  Line 534:
Origin or pseudonym:Main icefield
Mass (g):405.7
Class:Eu "pm"
Weathering grade:A/B
Ferrosilite (mol%):33-60
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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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     Catalogue of Meteorites:   (76° 43'S, 159° 40'E)
     Recommended::   (76° 43' 34"S, 159° 24' 37"E)
Note: the NHM and MetBase coordinates are 6.7 km apart

     This is 1 of 43700 approved meteorites from Antarctica (plus 3802 unapproved names)
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