Sample No.: ALHA77289

Location: Allan Hills

Field No.: 78010401

Weight (gms): 2186.0

Meteorite Type: Iron - Group I or Og

Physical Description:

The sample is angular and oblong (22x10x5 cm). It is orangish-brown and has many regmaglypts. The B surface has radial and transverse flow lines resulting from its orientation during atmospheric entry. The B surface also shows a zone of preferential melting (?) ~1 cm wide, that penetrates through the sample to the T surface. However, the zone of melting is only ~0.5 cm wide on the T surface.

Tentative Classification: Roy S. Clarke, Jr.

An area of approximately 25 cm² of macroetched surface was examined. Kamacite band widths are difficult to measure as the kamacite crystals tend to be stubby and irregular in outline. Estimated band widths are in the 2 to 3 mm range. Patches of α2 produced by atmospheric ablation are present along about half of the rim of the slice. Neumann bands are present. The dominant surface feature to the unaided eye is a highly speckled appearance due to abundant recrystallized kamacite fairly uniformly distributed over the surface. Modest amounts of grain boundary taenite and occasional small comb plessite areas are present. Schreibersite is present along grain boundaries. No large troilite or schreibersite are present and cohenite was not observed. External weathering is moderately severe. The specimen is a coarse octahedrite, a Group I or Og meteorite.