Spilite

Spilite (from Greek:σπιλάς) is a fine-grained igneous rock, resulting particularly from alteration of oceanic basalt.

The term was introduced into the geological literature by Alexandre Brongniart in 1827. Spilite is formed when basaltic lava reacts with seawater, or from hydrothermal alteration when seawater circulates through hot volcanic rocks.