Canvasite (rare) stoneware from Poona in India (40-60 mm)

Cavansite is a hydrated calcium vanadium silicate with the chemical formula Ca(V5+O)Si4O10 4H2O. This phyllosilicate, belonging to the mica group, exhibits a green to dark blue color with a vitreous luster, a blue-white streak color, and good cleavage along the [010] crystal plane. It has an average specific gravity of 2.25 and a hardness of 3 to 4. The crystal system is orthorhombic, and the mineral is not radioactive. The name cavansite is derived from the elements calcium, vanadium, and silicon in its composition. Cavansite is found chiefly in secondary mineralizations in andesites and basalts, the type locality being the area around the Owyhee Dam in Malheur County, Oregon, USA. The Wagholi Quarry near Poona, India, is the principal locality today.