tobermorite

{{Infobox mineral | name = Tobermorite | category = Silicate mineral, Calcium silicate hydrate | image = Tobermorite-t08-76a.jpg | caption = Crystalline mass of tobermorite | formula = Ca5Si6O16(OH)2·4H2O, or; Ca5Si6(O,OH)18·5H2O | IMAsymbol = Tbm | molweight = 702.36 g/mol | strunz = 9.DG.10 | system = Orthorhombic | class = Disphenoidal (222) H-M symbol: (2 2 2) | symmetry = C2221 (no. 20) | unit cell = a = 11.17 Å, b = 7.38 Å c = 22.94 Å; β = 90°; Z = 4 | color = Pale pinkish white, white, brown | habit = As minute laths; fibrous bundles, rosettes or sheaves, radiating or plumose, fine granular, massive. | twinning = | cleavage = {001} Perfect, {100} Imperfect | fracture = | tenacity = | mohs = 2.5 | luster = Vitreous, silky in fibrous aggregates | polish = | refractive = nα = 1.570 nβ = 1.571 nγ = 1.575 | opticalprop = Biaxial (+) | birefringence = δ = 0.005 | dispersion = | pleochroism = | fluorescence= Fluorescent, Short UV:weak white to yellow, Long UV:weak white to yellow | absorption = | streak = White | gravity = 2.423 – 2.458 | diaphaneity = Translucent to translucent | other = | references = }}

Tobermorite is a calcium silicate hydrate mineral with chemical formula: Ca5Si6O16(OH)2·4H2O or Ca5Si6(O,OH)18·5H2O.