serpentinite

ser pen tin ite |ˌsərpənˈtēnīt, -ˈtī -ˈsərpəntɪnaɪt | ▶noun Geology a dark, typically greenish metamorphic rock, consisting largely of serpentine or related minerals, formed when mafic igneous rocks are altered by water. ORIGIN 1930s: from serpentine + -ite 1 .

serpentinite

serpentinite |ˈsəːp (ə )ntɪˌnʌɪt | ▶noun [ mass noun ] Geology a dark, typically greenish metamorphic rock, consisting largely of serpentine or related minerals, formed when mafic igneous rocks are altered by water. ORIGIN 1930s: from serpentine + -ite 1 .