Cavansite

Cavansite and pentagonite, which are beautiful, rare hydrous vanadium silicate minerals, are known to be dimorphs of Ca(VO)(Si4O10)•4H2O. Thermal analyses performed on cavansite suggested that all the H2O molecules present in this mineral are zeolitic. However, H2O doesn't not present zeolitic in pentagonite which indicate that hydrous species play different roles in the structures of both minerals. Pentagonite is the high-temperature phase of canvasite (＞550℃）, whereas canvasite is the low-temperature phase (＜220℃）. No stable phase exists between this temperature range that are all aphanocrystallin. This is actually an interesting phenomenon in many late-hydrouthermal event that worked on secondary minerals. Example like the new mineral I found last year (paper in review), named molybdomenite-M2 which is a low-temperature phase of molybdomenite.

Although the type locality is Owyhee Da, Oregon, specimens from Wagholi, India are the best and most famous. In Wagholi, these minerals are present in abundance in the cavities of agglomerated breccias coexisting with Deccan basalts, where is a gigantic flood basalt plain that interests geologist a lot for studying mantle plume.

This 2.8cm pentagonite cluster I purchased in the mid 2019, the first piece I bought in Tucson (not the show) and 2 days before freshman journey began at U of A. Not the best piece I have seen but I valued these memories high.

Wagholi Quarries, Wagholi, Pune District, Pune Division, Maharashtra, India

Jingnan Zhang Coll, Jeff Scovil Photo