Luxullianite

Luxullianite (also Luxulyanite, Luxulianite) is a rare type of granite, notable for the presence of clusters of radially-arranged acicular tourmaline crystals enclosed by phenocrysts of orthoclase and quartz in a matrix of quartz, tourmaline, alkali feldspar, brown mica, and cassiterite.

Luxullianite from Cornwall, showing dark patches of tourmaline and pink crystals of orthoclase

Thin section of luxullianite from Cornwall, showing clusters of radially-arranged, acicular, greenish tourmaline crystals

The name originates from the village of Luxulyan in Cornwall, England, where this type of granite is found. An example may be seen in the Duke of Wellington's monument at St Paul's Cathedral in London.