Pentagonite

Cavansite is a relatively rare mineral. Initially found in cavities and veinlets in basalt and vugs in tuff at Owyhee Dam in Oregon, in 1960. It is polymorphic with the even rarer mineral, pentagonite, which is showing below. Previous studies suggest that cavansite is a low-temperature form and pentagonite a high-temperature form of the same mineral. Cavansite is a distinctive mineral and forms crystal aggregates, generally in the form of balls, up to a couple centimeters in size. Crystal aggregates consist of spherical rosettes with jutting pointed crystals. Sometimes the balls are coarse enough to allow the individual crystals to be seen. The colour of cavansite is distinctive, almost always a rich, bright blue. The color is the same as its dimorph, pentagonite, but the latter is generally sharper with bladed crystals. Finally, the associated minerals are useful for identification, as cavansite is frequently found sitting atop a matrix of zeolites or apophyllites. The colour is due to the V(IV) ion, which is always blue.

India is now a significant locality that produces the world best cavansite and petagonite. Although large amount of specimens were found in the past few decades, good ones are still rare. Today‘s production almost stagnates, thus most of these are from old finds. I am happy for getting a pretty matrix one in last year which compares to the first one I bought in 2019.

Pentagonite, 4.5cm, Wagholi Quarries, Wagholi, Pune District, Pune Division, Maharashtra, India

Jingnan (Tom) Zhang Coll & Photo