Sample No.: ALHA77283

Location: Allan Hills

Field No.: Y78010305

Weight (gms): 10510.0

Meteorite Type: Iron - Group I or Og

Physical Description:

Specimen is reddish brown to brown. The B surface is flat and the remainder of the sample is semi-rounded, suggesting that this is an oriented specimen. Radial and transverse flow marks are evident across all surfaces with the exception of the B. A few rounded holes from A cm to 3 cm in diameter are present on all surfaces. Some of these depressions are filled with dark gray material. Golden-brown patches ~3 mm in diameter are distributed over the meteorite's exterior surface. Ice was preserved in some of the regmaglypts when the sample was removed from the freezer. Approximate dimensions: 15.0x12.5x6.0 cm.

Tentative Classification: Roy S. Clarke, Jr.

An area of approximately 30 cm² of macroetched surface was examined. Kamacite band widths average approximately 1.8 mm with a length to width ratio ranging from 2 to 4. Neither Neumann bands nor ablation produced α2 were observed. Structures suggestive of shock deformation are present in the kamacite. Grain boundary taenite and comb plessite areas are abundant. The surface is dominated by an unusually large amount of uniformly distributed cohenite. The cohenite is badly shattered and plucked seriously during preparation of the slice. A large troilite-graphite inclusion is present, surrounded in turn by schreibersite and cohenite. Several schreibersite inclusions enclosed in cohenite are present in the kamacite near the troilite-graphite inclusion. Difficulty was encountered in sawing through several troilite-graphite areas. Where this happened, small black knobby protrusions were present within the carbon-rich areas. These observations suggest that these areas contain diamond. External weathering of this specimen appears to have been severe. This meteorite is a carbon-rich coarse octahedrite, a Group I or Og meteorite. It has characteristics that suggest it may be a fragment of a crater forming fall.