serpentinite

Green metamorphic rock consisting almost wholly of serpentine-group minerals which are essentially hydrous magnesium silicates; other constituents are usually present, producing veins and blotches of various colors. Its typical green color and mottled appearance explain its name which derives from the Latin 'serpentinus' meaning 'resembling a serpent.' Its color and ability to take a high polish have made serpentinites popular with many civilizations over time for decorative and ornamental work.