PENTAGONITE – Electric Blue Fan-Shaped Crystal Spray, Wagholi, Pune, India

This is a genuinely fine example of Pentagonite, one of the rarest and most coveted blue minerals in the collecting world, recovered from the celebrated basalt quarries of Wagholi, near Pune, in the Deccan Traps of Maharashtra, India — the only locality on Earth that has ever produced this species in fine, well-formed crystallized specimens. The piece is dominated by a spray of slender, acicular crystals that radiate outward from a common base into a striking fan-shaped cluster, a habit typical of the species and often the prelude to the more elaborate pseudo-pentagonal "fiveling" twins for which Pentagonite is named. The saturated, electric-blue color of the crystals contrasts dramatically against the paler zeolite matrix on which they rest, giving the specimen strong visual depth and genuine shelf presence.

Pentagonite is chemically identical to the far more common Cavansite, of which it is a rare dimorph — meaning the two minerals share an identical formula and composition but crystallize into different internal structures and, consequently, different external crystal shapes. While Cavansite typically forms compact, rounded rosettes, Pentagonite develops these more elongated, spiky, and dramatic sprays, and occurs at a ratio of roughly one specimen for every thousand pieces of Cavansite found at Wagholi, which explains the strong mineralogical interest in well-formed clusters despite their modest size.

The Wagholi quarry complex, comprising dozens of small basalt workings, has been actively studied and collected for decades and remains one of the world's classic secondary-mineral localities, though only a handful of the individual quarries there continue to yield good Cavansite and Pentagonite specimens, and recent geological research has noted that mining permits in the area are approaching their limits, making fine new material increasingly scarce. This specimen is completely natural and untreated, as described by the seller, and represents a genuine, high-value addition for any serious mineralogical collection.

Pentagonite is a rare hydrous calcium vanadium phyllosilicate with the formula Ca(VO)Si4O10·4H2O. Its intensely saturated electric-blue color is caused by the vanadyl cation (VO2+), a tetravalent vanadium-oxygen complex that occupies a specific structural site within the silicate framework and acts as a powerful chromophore — the same element responsible for the equally vivid blue of its far more common dimorph, Cavansite. Pentagonite forms as a secondary, low-temperature hydrothermal mineral, precipitating from silica- and vanadium-bearing fluids that percolate through gas vesicles and fracture zones in basalt and volcanic tuff, typically following the earlier crystallization of zeolites such as heulandite and stilbite on which it commonly rests. Its crystals grow as thin, sharply pointed acicular blades that radiate from a common point into fan-shaped or star-like sprays; when several individuals twin together around a shared axis, they can form the pseudo-pentagonal "fiveling" twins that give the species its name, now understood to consist of six intergrown crystals rather than the five originally assumed. Fine, well-crystallized Pentagonite is known almost exclusively from the Wagholi quarry complex near Pune, India, where only a few of the many basalt workings continue to yield good specimens and mining permits are reportedly approaching their limits, making high-quality new material increasingly scarce.

• Formula: Ca(VO)Si4O10·4H2O
• Key chemical elements: Calcium, Vanadium, Silicon, Oxygen, Hydrogen
• Hardness (Mohs scale): 3 to 4
• Mineral class: Phyllosilicates (Silicates)
• Crystal system: Orthorhombic
• Crystal habit: Acicular crystals radiating in fan-shaped sprays; pseudo-pentagonal fiveling twins
• Formation: Secondary hydrothermal mineral in basalt vesicles and fractures, associated with zeolites
• Color: Electric blue, caused by the vanadyl (VO2+) cation
• Locality status: Wagholi quarries, India — limited productive workings, mining permits reportedly approaching their limits

Pentagonite was first identified in 1973 from a small discovery near Owyhee Dam in Oregon, USA, where it occurred only as tiny, sub-millimetric twinned crystals — a far cry from the large, showy sprays later found in India. It is the rarer dimorph of Cavansite, sharing an identical chemical formula but crystallizing into a different, more elongated and elaborate habit; at Wagholi, well-formed Pentagonite is estimated to occur at a ratio of roughly one specimen for every thousand pieces of Cavansite found. The species owes its name to the pseudo-pentagonal, star-shaped outline created when its acicular crystals twin together into a "fiveling" — although recent mineralogical research published in 2025 revealed that these classic fivelings are actually formed by six intergrown individuals rather than five, overturning decades of assumption about the species' twinning.

In crystal healing traditions, Pentagonite is associated with the third eye and throat chakras and is believed by many practitioners to stimulate intuition, heighten psychic awareness, and support clarity of thought and communication. Its vivid electric-blue color is often linked to calm, centered energy, said to help quiet an overactive mind, dissolve negative thought patterns, and inspire fresh ideas and creative insight. As with all crystal healing practices, these interpretations are not scientifically proven.

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