Sample No.: ALHA77004

Location: Allan Hills

Field No.: 77122902

Weight (gms): 2230.0

Meteorite Type: H4 Chondrite

Physical Description:

The angular specimen, 7.0x5.5x2.0 cm, has many parallel fractures. Only the B surface has dull, brownish-black fusion crust. The other surfaces are weathered orangish-brown. Because of the severity of the weathering, it is impossible to define the shape, size, and color of the inclusions. When attempting to obtain a suitable thin section sample, the stone broke into six documented pieces. All pieces are severely weathered; no non-weathered surfaces were observed.

Petrographic Description: Brian Mason

The section shows well-developed chondritic structure, the chondrules ranging from 0.2-0.8 mm in diameter; a variety of types is present, the commonest being barred olivine, porphyritic olivine, and fine-grained or granular pyroxene. Much of the granular pyroxene is polysynthetically-twinned clinobronzite. Some of the chondrules are fragmented. The chondrules are set in a fine-grained granular matrix consisting largely of olivine and pyroxene, with minor amounts of nickel-iron and troilite (nickel-iron in greater amount than troilite). The section is pervaded with brown limonitic staining, and veins and patches of limonite are associated with many of the metal grains. Microprobe analyses show olivine with slightly variable composition (Fa18) and pyroxene with greater variability (Fs15-27, average Fs16).