First described in the carbonate blocks ejected by Mount Somma-Vesuvius (Italy, hence the name), with
occurrences also in Canada and California, it forms through contact metamorphism between limestones and magmatic intrusions (skarn), typically in Quaternary volcanic environments. Hardness 6–7 on the Mohs scale, density 3.3–3.5
g/cm³, color ranging from greenish-brown to yellow.

A historically significant mineral for Italian mineralogy and the scientific definition of skarn species; occasionally used in jewelry (the “californite” gem variety); highly sought after by collectors due to its Vesuvian type locality.