VESUVIANITE (according to the place of the find on the Vesuvius mountain), idocrase, wiluite (EN: vesuvianite, idocrase; DE: Vesuvian; FR: vesuvianite, vesuvienne; ES: vesuvianita; RU: везувиан), is the mineral of the sub-class of the insular silicates, Ca10(Mg,Fe)2Al4[SiO4]5[Si2O7]2(OH,F)4. Vesuvianite sometimes contains up to 3.5% of MnO, up to 4.7% of TiO2, up to 1.5% of Na2O, K2O, up to 1.5% of BeO; there have been identified within the vesuvianite from the skarns the Zn and Cu (cyprine, cupreous vesuvianite) impurities. Within certain vesuvianites, there exist B, Cr, Th, and radioactive elements. Vesuvianite crystallizes itself into the tetragonal crystal system. Vesuvianite forms the short-columnar, less often bipyramidal crystals, columnar and radial-radiant aggregates, dense and granular masses. Vesuvianite is dark-green, olive-green, greenish-brown, less often colourless. According to the colouration, they distinguish the varieties: reddish-brown variety is egeran, pale blue variety is cyprine, olive-green or grass-green variety is californite. The lustre is vitreous. Vesuvianite is translucent. The hardness is 6.5. The density is 3370 ± 50 kilograms per cubic metre.

Vesuvianite is the characteristic mineral of the contact-metamorphic rocks and skarns, may be found within the metamorphosed limestones with grossular, diopside, wollastonite, epidote, and so on, and also within serpentinites, chlorite schists, and so on. The transparent vesuvianites with the beautiful colouration may serve as the faceting material (for example, the golden-brown vesuvianite from the Laurentian mountains within Canada); as the ornamental stone, there is also used californite, which is imitating the noble jadeite and nephrite.