Regolith breccia
A rock formed when loose surface soil on an airless body was pressed into solid stone.
On the Moon and asteroids, endless impacts grind the surface into a layer of dust and rubble called regolith. When later impacts compress and weld this loose material together, the result is a regolith breccia: a rock made of soil. It contains fragments of many different rock types, glass beads and broken crystals, all cemented together.
Regolith breccias are prized because they preserve a record of the surface. Grains that lay exposed collected atoms from the solar wind, the stream of particles from the Sun, so these rocks often carry high levels of implanted noble gases. Some also hold tiny fragments of other meteorites that struck the surface. The howardite Kapoeta, which fell in South Sudan in 1942, is a classic regolith breccia from Vesta. NWA 7034, the Martian meteorite nicknamed "Black Beauty", is another, and many lunar meteorites are too.
Look for a cut face with a "light–dark" texture: pale fragments of many sizes set in a darker, fine-grained groundmass. The clasts are angular and varied. Confirming a regolith origin requires lab work, such as measuring solar-wind gases.
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