Sample No.: ALH84190

Location: Allan Hills

Weight (g): 7.9

Field No.: 2490

Dimensions (cm): 3x1.5x1

Meteorite Type: Achondrite (unique)

Macroscopic Description: Roberta Score

This specimen probably fits on a corner of a larger meteorite that is angular and has an ablation flange. The interior material is extensively weathered; any features present are disguised by oxidation.

Thin Section (,2) Description: Brian Mason

The section shows an aggregate of anhedral to subhedral grains, 0.06-0.5 mm across, of olivine and pyroxene, with about 15% of disseminated nickel-iron and minor amounts of plagioclase and troilite. The proportion of pyroxene to olivine is estimated as 4:1. Weathering is extensive, with veinlets and small areas of brown limonite throughout the section. Microprobe analyses give the following compositions: olivine, Fa4; plagioclase, An19; pyroxene, Wo3Fs6 (slightly variable) with one grain of diopside, Wo43Fs3, analysed. The meteorite is essentially identical with ALHA81187, which was considered to be an unique achondrite; in mineral compositions and texture these meteorites closely resemble inclusions in iron meteorites, such as in Campo del Cielo (Wlotzka and Jarosewich, Smithsonian Contrib. Earth Sci., No. 19, p. 104, 1977).