Sample No. ALHA78006

Location: Allan Hills

Field No.: 277

Weight (gms): 8.0

Meteorite Type: Howardite

Physical Description:

This is a nearly complete specimen (3.0 x 1.5 x 2.0 cm). Shiny black fusion crust covers all of the stone with the exception of portions of the E, W and S surfaces. There the sample is void of fusion crust, light to dark gray interior material is exposed. A non-weathered brecciated surface with no metal exposed was revealed upon leaving this stone in half.

Petrographic Description: Brain Mason

The thin section shows a complex breccia of angular fragments (grains up to 1 mm long) of pyroxene (orthopyroxene and pigeonite and plagioclase, with numerous polymineralic enclaves, set in a matrix of comminuted pyroxene and plagioclase. Accessory chromite and ilmenite and trace amounts of troilite and nickel-iron are present. The enclaves are holocrystalline pyroxene-plagioclase aggregates, and vary considerably in texture from coarse-grained gabbroic to fine-grained basaltic types. Slight weathering is indicated by small areas of rusty staining, usually in association with metal grains. Microprobe analyses show a wide range in pyroxene composition: Wo2-12En31-72Fs25-61; a number of grains with uniform composition Wo3En11Fs26 suggests the presence of a diogenitic component. Plagioclase averages An91. A single grain of iron-rich olivine (Fa81) was analyzed. The meteorite is classified as a polymict pyroxene-plagioclase achondrite (howardite).