Sample No.: ALHA77225

Location: Allan Hills

Field No.: 77122910

Weight (gms): 5878.0

Meteorite Type: H4 Chondrite

Physical Description:

This specimen has no fusion crust and is uniformly weathered and stained reddish-brown, however, some surfaces are more shiny than others. The sample is extremely fractured. One brassy colored clast is present on the T surface, possibly a troilite nodule. The B surface has what appears to be slickensides, but because of the severe weathering of the specimen it is impossible to determine this unambiguously. No un-weathered material is present on the exterior of the sample. When the specimen was cleaved it fell into many pieces and no unweathered material was exposed. Dimensions: 20 x 19 x 11 cm.

Petrographic Description: Brian Mason

Chondrules are numerous and well-defined, ranging from 0.5 to 1.8 mm in diameter; a variety of types is present, the commonest being porphyritic olivine and olivine pyroxene, barred olivine, and fine-grained radiating pyroxene. Much of the pyroxene in the olivine-pyroxene chondrules is polysynthetically twinned clinobronzite. Minor amounts of nickel-iron (~15%) and troilite (~5%) are distributed throughout the groundmass. The meteorite is extensively weathered, with limonite pervading the section and also concentrated in veinlets. Microprobe analyses show olivine (Fa17) and pyroxene (Fs16) of essentially uniform composition. The olivine and pyroxene composition and the presence of clinobronzite indicate that the meteorite can be classified as an H4 chondrite.