latite

or trachyandesite

Type of igneous rock that is abundant in western North America.

Usually white, yellowish, pinkish, or gray, it is the volcanic equivalent of monzonite. Latites contain plagioclase feldspar (andesine or oligoclase) as large, single crystals (phenocrysts) in a fine-grained matrix of orthoclase feldspar and augite.

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▪ geology

also called  trachyandesite 

      extrusive igneous rock very abundant in western North America. Usually coloured white, yellowish, pinkish, or gray, it is the volcanic equivalent of monzonite (q.v.). Latites contain plagioclase feldspar (andesine or oligoclase) as large, single crystals (phenocrysts) in a fine-grained matrix of orthoclase feldspar and augite. They also contain phenocrysts of diopside, and sometimes biotite and hornblende; accessory minerals include apatite, zircon, leucite, and magnetite. Latites are chemically intermediate to trachytes and andesites; when the matrix contains considerable quartz, the rock is transitional to dacite.

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