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Allan Hills A81187
Basic information Name: Allan Hills A81187
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA81187
This meteorite may also be called Allan Hills 81187 (ALH 81187) in publications.

Observed fall: No
Year found: 1981
Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)]
Mass:help 40 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 7(2)  (1984)  Achondrite
AMN 9(4)  (1986)  Achondrite-unique
AMN 17(1)  (1994)  Acapulco-like
Meteoritical Bulletin:  MB 76  (1994)  Acapulcoite
NHM Catalogue:  5th Edition  (2000)  Acapulcoite
MetBase:  v. 7.1  (2006)  Acapulcoite
Recommended:  Acapulcoite    [explanation]

This is 1 of 74 approved meteorites classified as Acapulcoite.   [show all]
Search for other: Acapulcoite-lodranite family, Acapulcoites, and Primitive achondrites
Writeuphelp
Writeup from AMN 7(2):

Sample No.: ALHA81187

Location: Allan Hills

Field No.: 1236

Weight (gms): 40.0

Meteorite Type: Achondrite (unclassified)/Forsterite Chondrite

Physical Description: Roberta Score

Fusion crust covers two surfaces, one of which contains remnants of flow features. Several cracks penetrate the mostly weathered interior of the stone. Dimensions: 4.5 x 2.5 x 2 cm

 

Petrographic Description: Brian Mason

The section shows an aggregate of anhedral to subhedral grains, 0.05-0.6 mm across, of pyroxene and olivine, with about 20% of disseminated nickel-iron and minor amounts of plagioclase, troilite, and schreibersite. The proportion of pyroxene to olivine is estimated at 4:1. Weathering is extensive, with veinlets and small areas of brown limonite throughout the section. Microprobe analyses give the following compositions: olivine, Fa4; pyroxene, Wo3Fs6.5; plagioclase, An18. The meteorite is tentatively considered to be an achondrite (unclassified), but it may belong to the small group of forsterite chondrites (Graham et al., Mineralogical Magazine, v. 41, p. 201, 1977).

Data from:
  MB76
  Table 2
  Line 710:
Origin or pseudonym:Main icefield
Mass (g):40
Class:Acap
Weathering grade:B/C
Fayalite (mol%):4
Ferrosilite (mol%):6.5
Comments:81187 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 7(2) (1984), 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' 34"S, 159° 19' 6"E)
Note: the NHM and MetBase coordinates are 9.3 km apart

Statistics:
     This is 1 of 38940 approved meteorites from Antarctica (plus 5051 unapproved names)
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