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Allan Hills A77081
Basic information Name: Allan Hills A77081
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77081
This meteorite may also be called Allan Hills 77081 (ALH 77081) in publications.

Observed fall: No
Year found: 1977
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 8.6 g
Antarctic Meteorite Newsletter:  AMN 1(2)  (1978)  Unclassified - possibly unique
AMN 2(1)  (1979)  H?
AMN 3(2)  (1980)  Achondrite
AMN 4(1)  (1981)  H?
AMN 13(1)  (1990)  H?/acapulco-like
AMN 17(1)  (1994)  Acapulco-like
Meteoritical Bulletin:  MB 76  (1994)  Acapulcoite
NHM Catalogue:  5th Edition  (2000)  Acapulcoite
NIPR Catalogue:  2000 Edition  (2000)  Unique(G)
MetBase:  v. 7.1  (2006)  Acapulcoite
Recommended:  Acapulcoite    [explanation]

This is 1 of 88 approved meteorites classified as Acapulcoite.   [show all]
Search for other: Acapulcoite-lodranite family, Acapulcoites, and Primitive achondrites
Writeup from AMN 4(1):

Sample No.: ALHA77081

Location: Allan Hills

Field No.: 77122716

Weight (gms): 8.59

Meteorite Type: H? Chondrite


Physical Description:

The stone is angular to subrounded. Highly weathered, brownish-black through reddish-brown fusion crust, and remnants of fusion crust, cover approximately 50 to 70% of the meteorite's surface. One face is a broken surface that shows iron oxide staining and has a granular texture. The longest side of the sample is ~2.0 cm.


Petrographic Description: Brian Mason

The meteorite is an equigranular (grains 0.1-0.3 mm across) aggregate of approximately equal amounts of olivine and orthopyroxene, with minor amounts of diopside, plagioclase, nickel-iron, and troilite, and accessory chromite. Fusion crust is present along one edge. A moderate amount of yellow-brown limonitic staining is present, concentrated around nickel-iron grains. Microprobe analyses show the minerals are uniform in composition: olivine, Fa11; orthopyroxene, Wo1.7Fs11En87; diopside, Wo45Fs5En50; plagioclase, An15, with 0.8% K2O.  The classification of this meteorite presents difficulties. The structure is achondritic, but the mineralogical composition is similar to that of the common chondrites, which suggests that this meteorite may be a completely recrystallized chondrite. However, the composition of the olivine and orthopyroxene is intermediate between that for the bronzite (H) and enstatite (E) chondrites. The meteorite resembles some silicate inclusions in iron meteorites. This meteorite is identical in mineral composition and structure to Acapulco, a recent Mexican fall.

Data from:
  Table 2
  Line 68:
Origin or pseudonym:Main icefield
Mass (g):8.6
Weathering grade:B
Fayalite (mol%):11
Ferrosilite (mol%):11
Comments:26Al=42±4; 77081 pairing group
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References: Published in Antarctic Meteorite Newsletter 4(1) (1981), 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'S, 159° 40'E)

     This is 1 of 43856 approved meteorites from Antarctica (plus 3802 unapproved names)
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