Cavansite
Cavansite is a rare hydrous calcium vanadium silicate, Ca(VO)Si4O10 4H2O, notable for an intense, almost electric blue color rarely matched by other minerals. It crystallizes in the orthorhombic system, typically as radiating clusters of thin blades lining cavities in basalt. First described in 1967, it remains one of the few common minerals containing vanadium as an essential structural element.
Cavansite properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | Ca(VO)Si4O10·4H2O |
| Mohs hardness | 3–4 |
| Crystal system | Orthorhombic |
| Luster | Vitreous |
| Streak | Pale blue |
| Cleavage | Perfect, one direction |
| Fracture | Uneven |
| Specific gravity | 2.21–2.31 |
| Transparency | Transparent to translucent |
| Common colors | Bright blue, Deep blue |
| Rarity | common |
Geology & background
Cavansite forms as a late-stage secondary mineral in gas cavities, or vesicles, within basaltic lava flows, precipitating from hydrothermal fluids alongside zeolites such as stilbite and heulandite once the surrounding rock had cooled and fractured. The type locality and by far the finest specimens come from the Deccan Traps basalt of Maharashtra, India, particularly quarries near Pune, where miners occasionally break into vesicles lined with sprays of vivid blue blades. A much smaller number of localities exist elsewhere, including basalt flows in Oregon, making Indian material the benchmark for the species among collectors.
Because good crystals are confined to a narrow geologic setting, cavansite specimens are essentially all recent finds rather than historic material, and quality varies enormously between individual pockets.
How to identify Cavansite
Cavansite is identified almost entirely by its saturated turquoise-to-cobalt blue color, unmatched by common minerals apart from the much softer azurite. It forms spherical or fan-shaped clusters of thin, radiating blades with a vitreous luster and a pale blue streak, and it has a hardness of 3 to 4, distinctly softer than the zeolites it often accompanies. Its close look-alike, pentagonite, shares the same chemistry but crystallizes in a different system with a slightly different blade arrangement, and the two can only be reliably separated with X-ray diffraction.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Cavansite is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Cavansite worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- Cavansite was first scientifically described only in 1967, making it a relatively recent addition to the mineral kingdom.
- Nearly all fine cavansite specimens in the world come from basalt quarries near Pune in Maharashtra, India.
- Cavansite shares its exact chemical formula with the rarer mineral pentagonite, which crystallizes in a different symmetry.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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