Martian basalt (shergottite). Found in 1999.
Dar al Gani 670
Libya
Found 1999
Martian basalt (shergottite)
A dark-brown stone, broken into three adjoining pieces, with a total mass of 1619 g was found in the Dar al Gani region. Mineralogy and classification (L. Folco, MNA-SI): centimeter-sized patches of fusion crust are present on the external surfaces; porphyritic texture consisting of millimeter-sized phenocrysts of brown olivine (Fo58–80) set in a fine grained basaltic groundmass of tabular pyroxene and interstitial feldspathic glass (An52–72Or0–1); pyroxene is primarily pigeonite (En56–66Wo9–13) with subordinate enstatite (En73–82Wo2– 3) and augite (En48–50Wo31–36); other minerals are chromite, titanian chromite, ilmenite, merrillite, and pyrrhotite; shock features include strong mosaicism and planar deformation in olivine, undulose extinction and twinning in pyroxene, and abundant impact-melt pockets and veinlets; pervasive veins filled in by calcite are due to terrestrial weathering. Oxygen isotopes (A. Sexton and I. A. F ranchi, OU): δ17O = +2.83‰, δ18O = +4.95‰, Δ17O = +0.26‰. The petrography and level of terrestrial weathering are essentially identical to those of DaG 476 and DaG 489, and the three are very likely paired. Specimens: main mass with anonymous finder; 11.9 g and one polished thin section at MNA-SI.
