Chondrite

Chondrules formed when clumps of dust in the solar nebula, the disc of gas and dust around the young Sun, melted briefly and solidified; chondrules, metal grains and dust then accreted into asteroids. Because chondrites come from bodies that never melted, their chemistry has changed little since the solar system formed, although most were later altered by heating or water on their parent asteroids. The different classes come from different asteroids. Ordinary chondrites, the most abundant class, make up about 74% of observed falls, according to the UCLA Meteorite Museum.

Freshly fallen chondrites have a thin black fusion crust, often with rounded thumbprint-like dimples, over a grey interior; weathering on Earth turns the crust rusty brown over decades or centuries. Chondrules (mean sizes about 0.3–1 mm) are visible on cut surfaces, and grinding a corner usually reveals tiny shiny flecks of metal. Most attract a magnet weakly, but magnetism alone does not prove a meteorite: magnetite, the material most often mistaken for meteorites, is magnetic and gives a black streak. Martian and lunar meteorites are achondrites, not chondrites. The Japanese retailer Pascle says most chondrite sold as beads is the Sahara meteorite NWA 869 and calls it Martian; the Meteoritical Bulletin, however, classifies Northwest Africa 869 (found 2000, about 2 t) as an L3-6 ordinary chondrite.