Sample No.: ALHA77190

Location: Allan Hills

Field No.: 77122915

Weight (gms): 387.1

Meteorite Type: H4 Chondrite

Physical Description:

The specimen is approximately 11.0x6.0x4.5 cm and is tabular. The N, T, and S surfaces have patchy remnants of thin, dull, black fusion crust. The E surface is highly oxidized, reddish-brown, fracture surface. The B surface is also a broken surface that is light brown. No unweathered material was exposed on the meteorite when it was cleaved in half. The sample is uniform reddish-brown throughout. After drying in the nitrogen cabinet for forth-eight hours, a small area of white material, presumably evaporites, developed on the freshly exposed interior surface.

Petrographic Description: Brian Mason

The section shows well-developed chondritic structure, but many chondrules appear to be partly fragmented (possibly shock-induced) and tend to merge with granular groundmass, which consists of olivine and pyroxene with minor amounts of nickel-iron and troilite. One large area of nickel-iron, 6x3 mm, was noted. The meteorite is severely weathered, with limonite veins throughout the section. Microprobe analyses show olivine with slightly variable composition (Fa17-19, average Fa18) and pyroxene with greater variability (Fs15-22, average Fs17). Accessory merrillite was identified with the microprobe. The meteorite is classified as an H4 chondrite.