komatiite

Oldest volcanic rock with three times as much magnesium as other volcanic rocks. Unlike basaltic lavas, which comprise oceanic crust, komatiites have the chemical composition of peridotite, the primary constituent rock of the upper mantle. Komatiites were extruded as a liquid at high temperatures, perhaps more than 1,600°C/2,912°F. They have low titanium and high magnesium, nickel, and chromium content.

Discovered in 1969 by Morris and Richard Viljoen, komatiites are named after the Komati River, Transvaal, South Africa, where they were first identified. The term is also used more loosely to refer to suites of other unusual basaltic rocks with which they are often associated.