Sample No.: ALHA77256

Location: Allan Hills

Field No.: Y78010310

Weight (gms): 676.2

Meteorite Type: Achondrite (diogenite)

Physical Description:

The sample is rounded with the fusion crust randomly distributed over approximately 15% of the surface. The remaining surface is free of fusion crust and appears to have been abraded away. The fusion crust is dull black. The surface area not covered with fusion crust is weathered and ranges from yellowish-brown to grayish-green. The various colors are limited to discrete areas. Several areas of iron oxide staining are present on the surface. This appears to be a complete stone. Approximate dimensions: 9.5x7.5x6.75 cm. Part of the specimen may be brecciated, and the thin section may not be representative of the entire meteorite.

Petrographic Description: Brian Mason

This meteorite consists almost entirely (~97%) of coarse (grains up to 6 mm) orthopyroxene clasts, with comminuted grain boundaries; microprobe analyses give the composition Wo2Fs23En75. Some orthopyroxene grains contain small blebs of clinopyroxene, with composition Wo46Fs8En46. Accessory minerals include plagioclase (~l%), troilite (<1%), and very rare minute grains of nickel-iron. A small area of limonite was noted, and moderate limonitic staining along grain boundaries. Meteorite ALHA77256 is a typical hypersthene achondrite (diogenite).