Sample No.: ALHA78040

Location: Allan Hills

Field No.: 284

Weight (gms): 211.7

Meteorite Type: Polymict Eucrite

Physical Description:

Snow and ice were present on the sample when it was removed from cold storage. This is a complete unweathered specimen (~9.0x5.0x3.0 cm). Black, shiny fusion crust ~.5 mm thick covers all the surfaces of the stone. The crust has been removed from the edges by spallation and has been preferentially weathered away on the surfaces in small circular areas. The B and T surfaces have had the most fusion crust removed, thus revealing light to medium gray matrix material that contains small (<1 mm) elongated white grains, probably feldspar. The T and S surfaces each have a 1.0 cm clast present. These clasts have a slightly lighter color than the surrounding fusion crust. On the N surface an oval vug is present. Inside this vug is a weathered yellowish-brown inclusion ~0.5 cm diameter that has a coarser texture than the surrounding matrix material. Cleaving this stone revealed a non-weathered surface with small (1-2 mm) dark gray minerals in the matrix material.

Petrographic Description: Brian Mason

The thin section shows a complex breccia of angular fragments, up to 1 mm long, of pyroxene (mostly pigeonite) and plagioclase, with numerous enclaves (the largest 3 mm across), in a matrix of comminuted pyroxene and plagioclase. The enclaves consist of pyroxene and plagioclase and range in texture from doleritic to gabbroic. Accessory chromite and ilmenite and trace amounts of troilite and nickel-iron are present. No evidence of weathering was seen. Fusion crust rims part of the section. Microprobe analyses show pigeonite ranging in composition from Wo6Fs33En61 to Wo7Fs52En41; a few grains of ferroaugite, averaging Wo33Fs40En27, were analysed. Plagioclase ranges in composition from An80 to An94 with an average of An86. The meteorite is classified as a polymict eucrite (pyroxene-plagioclase achondrite).