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Allan Hills A77307
Basic information Name: Allan Hills A77307
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77307
This meteorite may also be called Allan Hills 77307 (ALH 77307) in publications.

Observed fall: No
Year found: 1977 or 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 181.3 g
Antarctic Meteorite Newsletter:  AMN 1(3)  (1978)  C3
AMN 17(1)  (1994)  CO3?
Meteoritical Bulletin:  MB 76  (1994)  CO3?
NHM Catalogue:  5th Edition  (2000)  CO3
MetBase:  v. 7.1  (2006)  CO3.0-an
Antarctic Meteorite Newsletter:  AMN 31(1)  (2008)  CO3.0
Recommended:  CO3.0    [explanation]

This is 1 of 21 approved meteorites classified as CO3.0.   [show all]
Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 3), CM-CO clan chondrites, and CO chondrites
Writeup from AMN 1(3):
This text was reprinted from AMN 1(3) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: ALHA77307

Location: Allan Hills

Field No.: 78010702

Weight (gms): 181.3

Meteorite Type: Carbonaceous Chondrite - Type C-3


Physical Description:

The rounded specimen is covered with a dull black fusion crust 1-2 mm thick over post of the surface. Specimen is complete with the exception of one end where a fracture surface covers 1/8 of the specimen's total surface area. The fusion crust has polygonal fractures over most of the exterior surface. In a few places this fusion crust has been broken away revealing a black fine-grained matrix. Specimen shows several large fractures. On the surface neighboring one of these fractures there is a white material which may be an evaporite deposit. The side of the specimen that was in contact with the ice at the time of recovery is slightly reddish. Dimensions: 4.5 x 4.0 x 5.0 cm. Small, irregular white inclusions and several chondrules are apparent on a freshly broken surface.


Petrographic Description: Brain Mason

the section shows a closely-packed aggregate of mineral grains (up to 0.2 mm), mineral aggregates (up to 0.8 mm), and rather sparse small (0.1-0.5 mm) chondrules, set in a dark brown to black opaque matrix; the matrix makes up 40-50% of the section. The mineral grains, aggregates, and chondrules consist of olivine and polysynthetically-twinned clinopyroxene in approximately equal amounts. Microprobe analyses show that most of the olivine has forsterite composition, Fa~1, with a few grains ranging up to Fa30; the average for 30 grains is Fa5. The pyroxene is mostly clinoenstatite, Fs~l, but with a few more iron-rich grains. A little (1-2%) nickel-iron is present in the matrix as scattered grains, many partly altered to brown limonite. Fine-grained sulfide (~5%) is dispersed through the matrix. Fusion crust, 0.5 mm thick, is present along one edge of the section. The meteorite is a carbonaceous chondrite; an X-ray powder photograph shows that the matrix consists largely of olivine and pyroxene with some magnetite, which indicates a C3 classification.

Data from:
  Table 2
  Line 256:
Origin or pseudonym:Main icefield
Mass (g):181.3
Class:CO3 (?)
Weathering grade:Ae
Fayalite (mol%):1-30
Ferrosilite (mol%):1-12
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References: Published in Antarctic Meteorite Newsletter 1(3) (1978), 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 40129 approved meteorites from Antarctica (plus 4494 unapproved names)
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