Mineral
Okenita
Ca₃Si₆O₁₅·6H₂O · Silicatos (Filosilicatos)
Okenite is a low-temperature secondary formation occurring in cavities of volcanic rocks, growing as fibrous aggregates of thousands of microscopic needles, typical in the Deccan basalts of India.
Its spheres resemble cotton but consist of extremely fragile acicular crystals. Precipitation requires very specific humidity and internal chemistry. Growth takes place at low temperature within protected voids. Its delicate texture contrasts with the hardness of the host basalt.
In the Pune district, okenite and gyrolite develop in amygdaloidal cavities of the Deccan basalts. Yellowish stilbite commonly occurs in these associations. Its absence indicates deeper internal pockets with more stable hydrothermal circulation and less contamination by iron oxides.
Etymology
From the Greek "ōkénē" ("hair"), in allusion to its delicate silky fibres.