okenite

{{Infobox mineral | name = Okenite | image = Okenit, Gyrolith, Prehnit. Indien...2H1A6998OB.jpg | imagesize = 260 | alt = | caption = | category = Phyllosilicate minerals | formula = CaSi2O5·2H2O | IMAsymbol = Oke | strunz = 9.EA.40 | dana = | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | unit cell = a = 9.69, b = 7.28 c = 22.02 [Å]; α = 92.7° β = 100.1°, γ = 110.9°; Z = 2 | color = White, may show slightly yellow or blue tint | habit = Bladed crystals, typically fibrous, clusters of curved crystals and radial balls | twinning = Lamellar | cleavage = Perfect on {001} | fracture = Splintery | tenacity = Elastic | mohs = –5 | luster = Vitreous, pearly | streak = White | diaphaneity = Transparent, translucent | gravity = 2.28–2.33 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.512 – 1.532 nβ = 1.514 – 1.535 nγ = 1.515 – 1.542 | birefringence = δ = 0.003 – 0.010 | pleochroism = | 2V = Measured: 60° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Okenite (CaSi2O5·2H2O) is a silicate mineral that is usually associated with zeolites. It most commonly is found as small white "cotton ball" formations within basalt geodes. These formations are clusters of straight, radiating, fibrous crystals that are both bendable and fragile. It also belongs to the family of the calcium silicate hydrates (C-S-H) commonly found in hardened cement paste. In cement chemist notation (CCN) it is noted as CaO·2SiO2·2H2O and abbreviated as CS2H2.