Olivine-phyric shergottite
An olivine-phyric shergottite is a Martian basalt containing large olivine crystals in a finer groundmass.
An olivine-phyric shergottite is a Martian meteorite in which large olivine crystals, called phenocrysts, sit in a finer groundmass of pyroxene and maskelynite. 'Phyric' refers to this porphyritic texture of large crystals in a finer base.
These rocks are of interest because some may represent melts close to primitive Martian magma, little changed since leaving the mantle. Others contain olivine crystals that came from elsewhere and were picked up by the magma. Examples include Tissint, which fell in Morocco in 2011, Dhofar 019 and Yamato 980459, which has a glassy groundmass that suggests very rapid cooling.
Studying the zoning of olivine phenocrysts, and the chemistry of melt trapped inside them, lets scientists estimate the temperature and water content of Martian magmas and the conditions in the mantle where they formed. Tissint is particularly valued because it was a fresh fall, collected within months, and so is free of most desert weathering.
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