Dar al Gani 896

Libya

Found 2000 November

Achondrite (primitive, ungrouped)

A 22.6 g, dark, ~50% fusion crusted, stony fragment was found in Dar al Gani by a private collector. The specimen is moderately oxidized and irregularly fractured. On slicing, it shows an homogeneous lithology. Shock veins of dark glass cross-cut the entire specimen. Classification and mineralogy  (L. Folco, MNA-SI): abundant fine-grained, skeletal olivine crystals (Fo₈₂) are set in a mesostasis mainly consisting of rhyolitic glass plus quench crystallites of pigeonite (En54Wo9). Minor mineral constituents include enstatite (En₈₃Wo₂), augite (En₃₇Wo₃₀), and traces of chromite, sulfides, Fe-Ni metal and phospates. Undulose extinction and planar fracturing in olivine indicate moderate shock. Thin veins of secondary carbonates are present, most likely due to terrestrial weathering. Major element composition (P. Bland, OU) estimated from the mean of 256 broadbeam microprobe analyses (spot size 20 µm,) indicates a komatiitic IUGS composition (SiO₂ = 47.22 wt%, Na₂O + K₂O = 1.53 wt%, MgO = 29.87 wt%) with chondritic Mn/Mg 7.5 × 10⁻³. Oxygen isotopes (I. A. Franchi, OU): δ¹⁷O = +2.547‰, δ¹⁸O = +3.501‰, ∆¹⁷O = +0.726‰, similar to mean H chondrite. Data suggest an affinity with igneous inclusions in ordinary chondrites and impact melt origin. Specimens: main mass with anonymous finder; 5.442 g and four thin sections, MNA­SI.