Vesicles
Vesicles are small holes in a rock left behind by gas bubbles trapped as molten material solidified.
When molten rock contains dissolved gas and the pressure falls, the gas forms bubbles. If the melt solidifies before they escape, the bubbles are frozen in as round or oval cavities called vesicles. They are familiar in volcanic rocks such as pumice and some basalts.
Most meteorites have no vesicles at all, which makes this a useful identification clue. Asteroids are small and have little gravity, and many meteorite melts were low in gas, so bubbly textures are rare. Exceptions include some basaltic achondrites: Ibitira, a eucrite-like basalt that fell in Brazil in 1957, is well known for its vesicles. A few angrites and some impact-melt rocks also have them, and occasional tiny bubbles can appear in fusion crust, especially on the trailing side of an oriented meteorite.
For anyone checking a suspected meteorite, a rock riddled with holes is far more likely to be industrial slag or volcanic rock than a meteorite. Vesicles are easy to see with a hand lens: smooth-walled pits, often rounded, sometimes partly filled with later minerals. Their shape can even show which way the melt was flowing.
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