|Allan Hills A77290|
|Basic information||Name: Allan Hills A77290|
This is an OFFICIAL meteorite name.
This meteorite may also be called Allan Hills 77290 (ALH 77290) in publications.
Observed fall: No
Year found: 1977 or 1978
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass: 3.78 kg
This is 1 of 96 approved meteorites classified as Iron, IAB-MG. [show all]
Search for other: IAB complex irons, Iron meteorites, and Metal-rich meteorites
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.: ALHA77290
Location: Allan Hills
Field No.: Y78010505
Weight (gms): 3784.0
Meteorite Type: Iron - Group I or Og
Sample is subrounded to angular with a roughly tabular form. The entire specimen is covered with regmaglypts and is reddish to golden brown. From a field photo it was determined that the meteorite was sitting with the B surface on the ice. Irregular, dull metallic red splotches and a scaly iron oxide area, 7x5 cm, are present on the B-E surface. Present on the T surface is a ~2 cm depression containing a dull black material. Approximate dimensions: 15.5x16.0x6.0 cm.
Tentative Classification: Roy S. Clarke, Jr.
An area of approximately 70 cm2 of macroetched surface was examined. Kamacite band widths are in the 2 to 3 mm range with a length to width ratio of 2 to 4. Along most of one edge of the specimen, kamacite has been converted to α2 by atmospheric ablation. Neumann bands are present. Patches of recrystallized kamacite are sparsely distributed on the surface, and particularly concentrated around a large troilite-graphite inclusion that abuts only kamacite. Taenite is present at grain boundaries and in small comb plessite areas. Lamellar and grain boundary schreibersite are present. A kamacite area contains what appears to be partially decomposed cohenite surrounding a void that probably had contained schreibersite. The remnant of part of a troilite inclusion with bordering schreibersite is present at the edge of the slice. External weathering has been moderately severe. This specimen is a coarse octahedrite, a Group I or Og meteorite.
|References:||Published in Antarctic Meteorite Newsletter 3(2) (1980), JSC, Houston|
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
This is 1 of 36654 approved meteorites from Antarctica (plus 5519 unapproved names)
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