Sample No.: ALHA77290

Location: Allan Hills

Field No.: Y78010505

Weight (gms): 3784.0

Meteorite Type: Iron - Group I or Og

Physical Description:

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.