Sample No.: LEW86010

Location: Lewis Cliff

Weight (g): 6.9

Field No.: 4015

Dimensions (cm): 1.5 x 1.5 x 1.5

Meteorite Type: Achondrite (unique)

Macroscopic Description: Roberta Score

Greenish-brown crystals show relief on the exterior of this polished black specimen. Flow-like features are etched in the exterior. The interior is made-up of black shiny euhedral and anhedral platy crystals, clear anhedral crystals and green platy minerals. Oxidation is present.

Thin Section (,5) Description: Brian Mason

The section shows a granular aggregate of subequal amounts of plagioclase, pyroxene, and olivine, with a trace of opaques; plagioclase grains are up to 2.4 mm across, whereas the pyroxene and olivine grains are somewhat smaller, 0.6-1.2 mm. The pyroxene has a reddish-purple color, and is weakly pleochroic. The olivine shows widely spaced narrow (0.01 mm) exsolution lamellae (probably of kirschsteinite, Ca(Fe,Mg)SiO₄). Microprobe analyses give the following compositions: plagioclase, An₁₀₀ (K₂O, Na₂O both less than 0.1%); olivine, Fa₆₃, with 1.5-2.6% CaO; the pyroxene is a titanian fassaite, Wo₅₆Fs₁₉, with 10.4% Al₂O₃ and 2.4% TiO₂. One grain of kirschsteinite, (Ca₉₂Fe₈₆Mg₂₂)SiO₄, a grain of hercynite, (Fe₇₈Mg₂₂)Al₂O₄, and a grain of merrillite were analysed. The meteorite is a unique achondrite, but the mineral compositions indicate a close relationship to Angra dos Reis.