Nakhlite
A Martian meteorite made mainly of augite pyroxene crystals, formed in a lava flow or shallow intrusion on Mars.
Nakhlites are a group of Martian meteorites built mostly from green augite, a calcium-rich pyroxene, together with some olivine and a fine-grained groundmass. The crystals are elongated and often aligned, suggesting they settled in a thick lava flow or shallow magma body. Most nakhlites crystallised about 1.3 billion years ago, and their cosmic-ray exposure ages point to one impact that launched them all from Mars around 11 million years ago.
They are scientifically precious because many contain small amounts of iddingsite, a reddish mixture of clay, iron oxides and carbonate formed when liquid water seeped through the rock on Mars. That makes nakhlites direct evidence of water acting in the Martian crust. The group is named after Nakhla, which fell near Alexandria in Egypt on 28 June 1911 as a shower of around 40 stones. Lafayette and Governador Valadares are other classic members.
Nakhlites tend to be greenish-grey inside with a black crust. Under a hand lens, the elongated augite prisms may be visible. They are rare and valuable, so any suspected piece needs laboratory classification before claims are made.
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