Sample No.: ALHA78132

Location: Allan Hills

Field No.: 406

Weight (gms): 656.0

Meteorite Type: Polymict Eucrite

Physical Description:

Snow/Ice was present on the sample when it was removed from cold storage. This appears to be a complete specimen (11x10x8 cm) with vitreous black fusion crust on all sides. The overall shape is pyramidal with the B surface being flat. The fusion crust on the T surface has flow bands, most prominent in the N-S direction and less prominent in the W-E direction. The B surface has radial flow lines in area that is concave. The fusion crust on the S surface is much duller than on the rest of the stone. The crust has been spalled or chipped in some areas, revealing a medium gray interior material. Small (<1 mm) inclusions, both lighter and darker than the matrix are apparent. Several holes (voids) that penetrate the fusion crust by as much as ~1 cm were noted over the entire stone. One in particular is ~9 mm in diameter and ~1 cm deep and contains a yellowish grain (?) ~2 mm long. The cut face shows a light gray matrix dotted with rounded and irregular shaped grains (?) that are both lighter and darker than the matrix. The largest grain is ~.5 cm in diameter. The voids that are present on the exterior of this specimen did not appear in the interior. A vein (?) of white grains extends for 6 cm across the cut face in the W-E direction.

Petrographic Description: Brian Mason

The thin section shows a complex breccia of angular fragments (up to 1 mm across) of pyroxene (mostly pigeonite) and plagioclase, with numerous enclaves, in a matrix of comminuted pyroxene and plagioclase with accessory chromite and ilmenite. Most enclaves are ophitic to subophitic intergrowths of plagioclase and pyroxene, but one large elliptical one, 6 mm long, consists largely of pyroxene clasts. Microprobe analyses show pigeonite (with some augite exsolution lamellae) ranging in composition (Wo7-15Fs40-68), and plagioclase An78-81, average An88; the pyroxene in the pyroxene enclave has composition Wo6Fs32En62, and appears to be an inverted pigeonite. The meteorite is a pyroxene-plagioclase achondrite; its classification is a polymict eucrite.