Class : Silicates
    Subclass : Phyllosilicate
    Crystal system : Orthorhombic
    Chemistry : Ca(VO)Si₄O₁₀ . 4H₂O
    Rarity : Extremely rare

Pentagonite is an extremely rare mineral, dimorphic to cavansite and of a higher temperature than the latter. It is found in cracks, cavities and vacuoles of basalt breccias and andesitic tuffs where it is associated with various zeolites. It is a mineral that owes its name to its cyclic twin with a 5 pseudosymmetry order which produces pentagonal sections, however almost never observable in nature. Pentagonite is very similar to cavansite, it has the same bright blue color, the only difference is that its crystals are much more developed and can reach several centimeters. It presents as acicular crystals in the form of isolated fine blades or in a group then forming magnificent urchins and it is often associated with cavansite. Because it is vanadium-rich composition, it can theoretically constitute an ore of this element, however because of its color and its great rarity, it is a mineral much sought after by mineral collectors.

This mineral is not present in the French underground.

No fake inventories for this species, however, cavansites can sometimes be sold for pentagonite to justify higher prices, see our article on this here.