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Allan Hills A78261
Basic information Name: Allan Hills A78261
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA78261
This meteorite may also be called Allan Hills 78261 (ALH 78261) in publications.

Observed fall: No
Year found: 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 5.1 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 3(2)  (1980)  C2
AMN 17(1)  (1994)  CM2
Meteoritical Bulletin:  MB 76  (1994)  CM2
NHM Catalogue:  5th Edition  (2000)  CM2
MetBase:  v. 7.1  (2006)  CM2
Recommended:  CM2    [explanation]

This is 1 of 533 approved meteorites classified as CM2.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 2), CM chondrites, and CM-CO clan chondrites
Writeuphelp
Writeup from AMN 3(2):
This text was reprinted from AMN 3(2) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: ALHA78261

Location: Allan Hills

Field No.: 491

Weight (gms): 5.113

Meteorite Type: Carbonaceous Chondrite - C2

 

Physical Description:

This triangular sample (2.5 x 1.5 x 1.0 cm) is totally covered with thin, dull, black, polygonally fractured fusion crust, except along the edges where the fusion crust has abraded away. The matrix revealed in these areas is greenish-black and has small (<1 mm) rounded and irregular white clasts throughout. Small voids, as much as 1 mm in diameter, are present on two surfaces. Chipping of the specimen during processing revealed abundant rounded and irregular inclusions in the meteorite.

 

Petrographic Description: Brian Mason

The section shows numerous tiny grains (up to 0.1 mm) and irregular aggregates (up to 0.3 mm) of olivine and polysynthetically twinned clinopyroxene, and a few small chondrules, in a translucent isotropic olive-brown matrix. The section contains very little troilite as minute scattered grains, and a little nickel-iron as inclusions in the chondrules. Porous fusion crust up to 2.5 mm thick rims part of the section. Microprobe analyses show that both olivine and pyroxene have variable composition. Olivine ranges from Fa0 to Fa50, with an average of Fa6; it has a notable chromium content, Cr2O3 ranging from 0.3-0.6 weight percent. Pyroxene is generally close to clinoenstatite in composition, ranging from Fs1 to Fs8, with an average of Fs7. This meteorite is a carbonaceous (C2) chondrite, and shows a close similarity to ALHA77306.

Data from:
  MB76
  Table 2
  Line 437:
Origin or pseudonym:Main icefield
Mass (g):5.1
Class:CM2
Weathering grade:A
Fayalite (mol%):0-50
Ferrosilite (mol%):1-8
Comments:81002 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 3(2) (1980), 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° 43'S, 159° 40'E)

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