Fusion crust colour
Fresh fusion crust is usually black and may be matte or glossy; it turns brown as the meteorite weathers.
A meteorite's fusion crust is the thin layer of melted rock left on its surface after its fiery passage through the atmosphere. Its colour and texture give clues to the meteorite's type and age on Earth.
Fresh crust on most stony meteorites is black and matte, sometimes with a faint sheen. On calcium-rich achondrites, such as eucrites and angrites, the crust is often glossy and shiny, like a black glaze, because their melted material forms glass more easily. Aubrites, which are very low in iron, can have a pale, honey-coloured or greyish crust. Iron meteorites have a thin, bluish-black crust when fresh.
Once on Earth, crust weathers. Within months to years it may turn dull brown as iron rusts, and in deserts it can be sandblasted away. A black, crisp crust suggests a recent fall, while a brown, patchy one suggests a long stay on the ground. Do not scrub crust off a specimen: it is part of its story.
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Level: Explorer Ages 10 and up