Vesuvianite n. : A mineral occurring in tetragonal crystals, and also massive, of a brown to green color, rarely sulphur yellow and blue. It is a silicate of alumina and lime with some iron magnesia, and is common at Vesuvius. Also called idocrase.

Example:


Taxonomy
Vesuvianite, minerals, free encyclopedia, idocrase, search, Ca10, SiO4, Si2O7, gm, columnar, conchoidal, hardness, Vitreous, resinous, Diaphaneity, Optical properties, Uniaxial, colored varieties.

Defination from the web:
Vesuvianite, also known as idocrase is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism. ... Retrieved from "http://en.wikipedia.org/wiki/Vesuvianite" ...