Vesuvianite, a complex magnesium iron silicate that was named after its occurrence on the famous Italian volcano, Vesuvius, is also known in the mineral literature as idocrase. It occurs worldwide, along with grossular garnet, in rocks derived from altered limestone, known as skarns. Vesuvianite is tetragonal, that is, displays four-fold symmetry, well exemplified by these excellent crystals from Morelos, Mexico.