Cavansite - Encyclopedia

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


Cavansite is a very rare mineral, dimorphic to pentagonite and lower in temperature. 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 chemical composition : calcium, vanadium and silicon. Cavansite is particularly spectacular because of its splendid blue color sustained in blue-green. It presents itself in aesthetic spherulitic rosettes rarely exceeding one centimeter and composed of millimetric prismatic crystals. Due to its vanadium rich composition, it can theoretically be an ore of this element, however because of its color and its relative rarity, it is a mineral sought after by mineral collectors.

Cavansite floater with calcite from Poona, India
Cavansite ball on stilbite cups from Poona, India
Cavansite and calcite from Poona, India
Large calcite crystal with cavansite balls from Poona, India

Cavansite in the World

The best specimens of cavansite all come from Wagholi basalt quarries near Poona, India, and are the best known specimens with centimetric bright blue balls on stilbite, sometimes associated with rhombohedral crystals of slightly yellow calcite. Groups of balls can form clusters of more than 5 cm, sometimes floaters.

Cavansites are also found anecdotally in Aranga quarry in New Zealand, in 1 mm blue spherules associated with calcite and chabazite.
 
Cavansite is also reported in the USA at Owyhee Dam, Malheur Co., Oregon, the type-locality, in 2 mm spherules on calcite, stilbite and heulandite.

Cavansite in France

This mineral is not present in the French underground.

Twinning and special forms

Unlike its dimorphic pentagonite, no twin exists for cavansite.

Fakes and scams

No fake inventories for this species, sometimes sold for pentagonite to justify higher prices, see our article here.



Hardness : 3 to 4
Density : 2.21 to 2.31
Fracture : Fibrous
Streak : White-blue



TP : Translucent to transparent
IR : 1.542 to 1.551
Birefringence : 0.009
Optical character : Biaxial +
Pleochroism : Blue to green
Fluorescence : None


Solubility : Acids

Magnetism : None
Radioactivity : None