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Allan Hills A77272
Basic information Name: Allan Hills A77272
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77272
This meteorite may also be called Allan Hills 77272 (ALH 77272) in publications.

Observed fall: No
Year found: 1977 or 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 674 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 1(2)  (1978)  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 4(1):

Sample No.: ALHA77272

Location: Allan Hills

Field No.: Y78010509

Weight (gms): 674.1

Meteorite Type: L6 Chondrite

 

Physical Description:

Specimen is angular in shape. A thin, ~l mm thick, black fusion crust covers approximately 50% of the meteorite. The crust appears moderately stained, probably by an iron oxide weathering rind. Several large surface fractures are present. The S surface, which is covered by a fusion crust, is concave. The remaining 50% of the specimen is a fracture surface that is yellowish-brown. More than 2 of the fracture surface is iron oxide stained. Where this is not present, the matrix is a fine grained, whitish-gray material. Several very fine grained, rounded inclusions are apparent on the fracture surface. This is not a complete specimen. From the field photos it was determined that the B surface was in contact with the aluminum foil. It is not known if this surface (B) was in contact with the ice prior to placement on the foil. The broken surface produced during chipping showed only oxidized metal.

 

Petrographic Description: Elbert King

This meteorite contains abundant fresh metal and troilite. One troilite grain is more than 4 mm in maximum dimension. Many metal and troilite grains show alteration to hematite and limonite/goethite, and some metal and troilite grains include thin veins of oxide alteration. However, the overall appearance of the meteorite is fresh and oxidation of the metal and troilite is scattered, not pervasive. Chondrule outlines and margins are indistinct, but some barred and radiating chondrule structures are clearly visible. The largest chondrule still visible in this section (total area less than 1 cm2) has a maximum diameter of approximately 1.6 mm. No fresh glass was seen in the chondrules or matrix. In fact, some areas that appear to have been glass are now coarsely crystalline. Several of the chondrules have the textures of fluid drop chondrules, but the meteorite is so recrystallized that no lithic chondrules can now be recognized. One chondrule is recrystallized such that its margin cannot be recognized except by an outline of small troilite grains. Most of the larger olivine and pyroxene grains have very patchy and undulatory extinction. Some mineral grains show physical dislocations. Also apparent are numerous closely spaced fractures in some mineral grains. It seems likely that the meteorite has experienced light to moderate shock. The largest single crystals of olivine are more than 1 mm maximum dimension. Grains of plagioclase (oligoclase?) with prominent twinning are common. No unusual textural features were observed in this section. Electron microprobe analysis of five olivines shows that it is close to Fa26.

Data from:
  MB76
  Table 2
  Line 223:
Origin or pseudonym:Main icefield
Mass (g):674.1
Class:L6
Weathering grade:B/C
Fayalite (mol%):24
Ferrosilite (mol%):20
Comments:26Al=35±4; 77272 pairing group
Catalogs:
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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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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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