Onyx

Onyx is a sedimentary rock formed by the precipitation of calcium carbonate in very still underground settings (grottos).
It is characteristically translucent with variegated veins of differing dimensions, generally having shades of brown, that give this marble a multi-colored appearance.
Onyx has always been associated with decorations given its transparent and multi-color appearance; unique aesthetic effects can be achieved when onyx is back-lit with neon or led lighting. Onyx is essentially used in interiors.