Formula: Ca₁₀(Mg, Fe)₂Al₄(SiO₄)₅(Si₂O₇)₂(OH,F)₄  The formula is a partial simplification of the full structural formula.

Species: Silicates – (Sorosilicates)

Colour: Brown, yellow, brown-black, light green, emerald green, white, red, purple, violet, blue-green to blue

Lustre: Vitreous, Resinous

Hardness: 6½

Specific Gravity: 3.32 – 3.43

Crystal System: Tetragonal

Member of: Vesuvianite Group

Name: Originally named “hyacinthus dictus octodecahedricus” by Moritz Anton Kappeler in 1723. Renamed “hyacinte du Vesuve” by Jean-Baptiste Louis Romé de L’Isle in 1772. This was possibly the inspiration for Abraham Gottlob Werner to rename the species “vesuvian” in 1795, after its discovery locality, Mount Vesuvius, Campania, Italy. In 1799, Rene Just Haüy introduced the name “idocrase”, which was formerly a popular name.

Type Locality: Mount Somma, Somma-Vesuvius Complex, Naples, Campania – Italy

Isostructural with: Fluorvesuvianite, Manganvesuvianite, Wiluite. Hydroxyl analogue of Fluorvesuvianite.