Hawaiite

It occurs during the later stages of volcanic activity on oceanic islands such as Hawaii,[2] which happens to be when the alkali metals are most present.

[3] In gemology, hawaiite is a colloquial term for Hawaii-originated peridot, which is a gem-quality form of the mineral olivine.

It is often impractical to determine the mineral composition of such a fine-grained rock, and so hawaiite is defined chemically.

However, hawaiite is composed mostly of andesine (plagioclase feldspar with an albite content of 50% to 70%) and pyroxene with smaller amounts of olivine.

[9] Other settings in which hawaiite and other alkaline volcanic rocks are found include regions of continental extension, such as the Basin and Range Province of western North America[10] and the Red Sea Rift.