15 articles
Adakite
Adakite is a group of igneous rocks defined by trace-element chemistry, named in 1990 after Adak Island magnesian andesites, and associated with porphyry copper deposits.
Alkali basalt
Alkali basalt is a fine-grained volcanic rock of basaltic silica content that is undersaturated in silica, defined by nepheline in its CIPW norm and typical of ocean-island and intraplate volcanism.
Anorthosite
Anorthosite is a coarse-grained plutonic igneous rock made almost entirely of plagioclase feldspar. Rare on Earth, it forms the Moon's bright highlands and hosts ilmenite deposits.
Carbonatite
Carbonatite is a rare igneous rock composed mainly of carbonate minerals, derived from Earth's mantle, and the primary source of niobium and light rare earth elements worldwide.
Dunite
Dunite is a coarse-grained ultramafic igneous rock of more than 90 percent olivine, named by Ferdinand von Hochstetter in 1859 after New Zealand's Dun Mountain.
Granodiorite
Granodiorite is a coarse-grained intrusive igneous rock intermediate between granite and diorite, defined by more plagioclase than potassium feldspar; the Rosetta Stone is a famous example.
Hyaloclastite
Hyaloclastite is a volcanic rock made of sharp-edged glass fragments that form when lava cools so fast on contact with water or ice that it shatters.
Lamproite
Lamproite is a rare ultrapotassic alkaline igneous rock derived from metasomatized lithospheric mantle, one of two rock types hosting economic primary diamonds, recognized after the Argyle discovery in 1979.
Latite
Latite is a volcanic rock made of roughly equal alkali feldspar and sodic plagioclase with little or no quartz, making it the extrusive equivalent of monzonite.
Monzogranite
Monzogranite is a variety of granite, a coarse-grained plutonic igneous rock containing 20 to 60 percent quartz and roughly equal amounts of alkali feldspar and plagioclase, defined in the QAPF classification.
Monzonite
Monzonite is a coarse-grained plutonic igneous rock in which alkali feldspar and plagioclase occur in roughly equal amounts, with little quartz; it sits between syenite and diorite.
Syenite
Syenite is a coarse-grained plutonic igneous rock composed mainly of alkali feldspar with little or no quartz, the quartz-poor counterpart of granite, named after Syene, Egypt.
Tholeiitic basalt
Tholeiitic basalt is a silica-saturated variety of basalt, defined by hypersthene among its pyroxenes, and is the dominant basalt of the ocean floor and of flood-basalt provinces such as the Columbia River Basalt Group.
Tonalite
Tonalite is a coarse-grained plutonic igneous rock consisting of quartz and plagioclase, usually with biotite and amphibole, and little alkali feldspar; it is named after Tonale Pass in the Alps.
Trondhjemite
Trondhjemite is a leucocratic intrusive igneous rock, defined as a tonalite with mafic minerals below 10 percent, named by Victor Moritz Goldschmidt in 1916 after Trondheim, Norway.