What is Okenite?
Okenite is a delicate hydrous calcium silicate famous for white silky spheres and fibrous sprays in basalt cavities.
Mineralogy and crystal structure
Reference formula: Ca10Si18O46·18H2O. Okenite has a hydrated triclinic framework and soft fibrous aggregates. The COD model represents an ordered structure, while natural water content and surface texture may vary. Okenite is classified with silicates and has a triclinic crystal system. Typical hardness is 4.5–5 on the Mohs scale and specific gravity is approximately 2.3–2.4.
Colour, lustre and habit
Typical colours include white, colourless, pale blue. The usual fibrous, radiating, botryoidal habit and silky, pearly, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Okenite forms in or is associated with low-temperature hydrothermal cavities in basalt and zeolite-rich volcanic rocks. Important documented localities include India, Iceland, Greenland, Scotland, the United States and New Zealand.
Silky white sprays in a basalt cavity
Okenite is a tactile-looking mineral that should be admired rather than touched. Its fragile fibres make the familiar volcanic cavity association part of its identity.
Collecting and care
Never scrub or soak; protect from impact, dust and humidity changes, and display behind a case or in a stable box.
