Northwest Africa (NWA) 10637 is a very rare type of stone meteorite known as a brachinite. Most stone meteorites originated on asteroids and most art part of the large group known as chondrites. Chondrites are named after the chondrules (small, glassy spheres) that they contain.
Much more scarce than chondrites are the achondrites — stone meteorites without chondrules — and brachinites are part of this group. Brachinites take their name from the Brachina meteorite found in 1974 in Brachina, Australia. Only about 1 out of every 1,300 recovered meteorites is a brachinite, making them one of the rarest types known to science. Brachinites are mostly made up of the mineral olivine which, in its pure gemstone form, is known as peridot. That gives the greenish hue which can been seen in specimens, like this one, that have been sliced and polished in the laboratory.
Only one piece of NWA 10637 was found. Before cutting, its weight was only 554 grams, so examples of this brachinite are extremely rare. NWA 10637 consists of 87% olivine, with the rest being the mineral pyroxene, along with tiny veins of nickel-iron.
This 5.1-gram, laboratory-prepared full slice shows an attractive black, orange, and olive green matrix.