Antarctic Search for Meteorites (ANSMET) Search this
Weight:
9.954 g
Place:
Antarctica
Collection Date:
1977
Notes:
# NASA data for ALH 77257 Weathering: Ae Fracturing: B Fa: 14 mol % Fs: 12 mol % ²⁶Al: 38.7 ± 1.5 dpm/kg
Approximately one-half of the sample's surface is rounded and mostly covered with fusion crust ~2 mm thick. This crust is dark brown with areas of reddish (iron oxide?) staining. Small areas of the fusion crust have been plucked revealing crystalline structure. The remaining two-thirds of the sample consists of three planes which are fracture surfaces. These surfaces are crystalline, rough on a mm scale, and show no evidence of fusion crust. The fracture surfaces are dark brownish-black and are moderately weathered with small patches of what appears to be iron oxide stain. Crystalline grains with well-developed crystal faces set in a black, fine-grained matrix make up the broken surface. Some grains are covered with a dark stain and others are milky white to clear. The small, white to clear anhedral grains are aligned in a strip across the broken surface (N & T views) and part of the fusion crust. The sample is not a complete stone. The small white anhedral grains are visible on the surface of the meteorite in the field photos. One grain was removed and placed in an aluminum cup and allowed to warm. The grain retained its original form after an hour of warm temperature.