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Allan Hills A77270
Basic information Name: Allan Hills A77270
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77270
This meteorite may also be called Allan Hills 77270 (ALH 77270) in publications.

Observed fall: No
Year found: 1977 or 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 589 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 2(1)  (1979)  L6
Meteoritical Bulletin:  MB 76  (1994)  L6
NHM Catalogue:  5th Edition  (2000)  L6
MetBase:  v. 7.1  (2006)  L6
Recommended:  L6    [explanation]

This is 1 of 10989 approved meteorites (plus 6 unapproved names) classified as L6.   [show all]
Search for other: L chondrites, L chondrites (type 4-7), Ordinary chondrites, and Ordinary chondrites (type 4-7)
Writeuphelp
Writeup from AMN 2(1):
This text was reprinted from AMN 2(1) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: ALHA77270

Location: Allan Hills

Field No.: Y78010502

Weight (gms): 588.9

Meteorite Type: L6 Chondrite

 

Physical Description:

The sample is pyramidal, with the B surface flat, approximately 90% of the specimen is covered with a dull, brownish-black fusion crust, approximately 0.5 mm thick. The surfaces not covered with fusion crust have a weathering rind. The sample has a few fractures. The specimen measures 11.0x7.0x6.0 cm. When obtaining a suitable sample for thin section preparation, whitish-gray matrix material with small metallic flakes was exposed. After the sample was cleaved into halves, it became obvious that weathering along the fractures is severe. In non-fractured areas, the weathering rind penetrates 1 to 3 mm below the fusion crust.

 

Petrographic Description: Brian Mason

The section shows sparse and poorly-defined chondrules, merging with the granular groundmass, which consists of olivine and pyroxene, with minor sub-equal amounts of nickel-iron and troilite; occasional small grains of plagioclase were noted. Fusion crust, up to 0.9 thick, rims part of the section. Limonitic straining and occasional grains of limonite occur in association with nickel-iron grains. Microprobe analyses show olivine (Fa24), orthopyroxene (Fs21), and plagioclase (An11) of uniform composition; a little diopside (Wo46En45Fs9) was noted in association with orthopyroxene. The meteorite is classified as an L6 chondrite.

Data from:
  MB76
  Table 2
  Line 221:
Origin or pseudonym:Main icefield
Mass (g):588.9
Class:L6
Weathering grade:A/B
Fayalite (mol%):24
Ferrosilite (mol%):21
Comments:26Al=40±3
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 2(1) (1979), 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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