Catalog Search Guide
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Okenite
Okenite is a hydrated calcium silicate, chemically CaSi2O5·2H2O, prized by collectors for one of the most distinctive habits in the mineral kingdom: dense, fragile sprays of fine acicular fibers that bundle into radiating "cotton ball" or "sea urchin" clusters. Crystallizing in the triclinic system with a Mohs hardness of only 4.5 to 5, its fibers are surprisingly elastic and bendable, yet easily crushed if handled roughly, a tenacity tied to its perfect one-directional cleavage and weakly bonded layered structure. Colorless to snow-white, occasionally with a pale yellow or blue tint, okenite has a pearly to vitreous luster and forms as a secondary mineral lining vesicles and geodes in basalt, crystallizing from silica-rich fluids during the low-temperature alteration of volcanic rock.
The species was first described in 1828 from Disko Island, Greenland, and named after German naturalist Lorenz Oken, but it was the discovery of extraordinary material in the Deccan Traps of Maharashtra, India, that made okenite a true showpiece for collectors. The quarries of Poona (Pune) and Khandivali near Mumbai have yielded the world's finest specimens: subspheric balls of needle-thin crystals exceeding 5 cm in diameter, sometimes found nestled inside transparent optical calcite, and closely associated with stilbite, apophyllite, gyrolite, prehnite, laumontite, goosecreekite and chalcedony within the same basalt cavities. Beyond India, okenite is also documented from Bulla Island in Azerbaijan, Aranga in New Zealand, Disko Island and other Greenland localities, Bordo Island in the Faroe Islands, Iceland, Ireland, Chile, and a scattering of Alpine and North American occurrences including New Jersey.
For collectors, Okenite occupies a special niche among zeolite-suite minerals: it has no industrial use whatsoever and exists purely as a display and study specimen, valued entirely for its sculptural, almost botanical appearance. Fine Indian cotton-ball clusters remain the benchmark for the species, commanding strong prices for well-formed, undamaged balls, while the rarer optical calcite hosting internal okenite puffs and material from classic type localities like Disko Island add historical and scientific interest. Its combination of rarity, fragility, and unmistakable habit makes okenite a favorite centerpiece among calcium silicate and basalt-cavity mineral specimens.
