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.

Localities which have yielded fine crystallized specimens include Mount Vesuvius and the Ala Valley near Turin, Piedmont.

The name "vesuvianite" was given by Abraham Gottlob Werner in 1795, because fine crystals of the mineral are found at Vesuvius; these are brown in color and occur in the ejected limestone blocks of Monte Somma.

[5] A sky bluish variety known as cyprine has been reported from Franklin, New Jersey and other locations; the blue is due to impurities of copper in a complex calcium aluminum sorosilicate.