Sample No.: ALHA81012

Location: Allan Hills

Field No.: 1490

Weight (gms): 36.6

Meteorite Type: Eucrite

Physical Description: Roberta Score

Flow marks are present on the shiny black fusion crust which covers 75% of ALHA81012. Small clasts (<2 mm) are abundant in the light gray interior matrix. A few areas have oxidized to an orangish-brown color. Dimensions: 5 x 2 x 3 cm.

Petrographic Description: Brian Mason

The section consists largely of brown grains of pigeonite up to 0.9 mm and colorless grains of plagioclase up to 0.6 mm in a comminuted groundmass of these minerals. A few lithic clasts, up to 2.5 mm across, are present; most show ophitic textures. Fusion crust is present along one edge. Microprobe analyses show pyroxene compositions ranging fairly continuously from Wo3En35Fs62 to Wo35En32Fs33; En content shows a limited range (30-40) except for one grain Wo8En48Fs44. Plagioclase composition range is An84-94, mean An89. The meteorite is a eucrite, but it differs from previously described eucrites from the Allan Hills in the range and distribution of pyroxene compositions. It resembles ALHA81009 closely and is tentatively paired with that meteorite.