Cavansite

it's blue.

Cavansite is CAlcium VANadium SIlicate. Although it’s probably most famous from locations in India, the type locality of cavansite is Owyhee Dam, Malheur County, Oregon, USA, where it occurs in cavities in basalt and other volcanic rocks. The occurrence in India is very similar, although the basalts there are about 66 million years old in comparison to those in Oregon, which are part of the Columbia Plateau basalts, erupted beginning about 17 million years ago.  

Cavansite, Ca(VO)Si₄O₁₀ · 4H₂O, is dimorphous with pentagonite, meaning the two minerals have identical chemistry but different crystallography – in this case, rather slightly different crystallography. Cavansite is orthorhombic dipyramidal and pentagonite is orthorhombic pyramidal, meaning pentagonite does not have a mirror plane of symmetry across its crystallographic c axis. In practice the two minerals are very similar and hard to distinguish, although subtle color differences are reported. Pentagonite got its name for its typical five-fold habit reflecting twinning, but it still looks a lot like clusters of cavansite.

Ishida and others (2009, Polymorphic relation between cavansite and pentagonite: Genetic implications of oxonium ion in cavansite: Journal of Mineralogical and Petrological Sciences, 104 (4) 241-252) suggested that cavansite might be a low-temperature form compared to higher temperature pentagonite, and that some of the water in the cavansite structure is in the form of hydronium (H₃O⁺) and hydroxyl (OH) ions rather than simply H₂O. Whatever the difference, it’s pretty subtle.

And whatever the differences, they’re both pretty minerals. Below is an example labeled pentagonite. The broken cluster, about 5 mm across, has a crude radial habit like cavansite often shows more perfectly; this one is maybe a little less intensely blue, but for me, it’s really virtually identical to cavansite.