scawtite

{{infobox mineral | name = Scawtite | image = Scawtite.jpg | alt = | caption = | category = Silicate mineral | formula = Ca7(Si3O9)2CO3·2H2O | IMAsymbol = Scw | strunz = 9.CK.15 | dana = 64.2.1.1 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m | unit cell = a = 10.12 Å, b = 15.18 Å c = 6.62 Å; β = 100.55°; Z = 2 | color = Colorless | habit = Platy - micaceous, parallel to radiating clusters | twinning = | cleavage = Perfect on {001}, poor on {010} | fracture = | tenacity = | mohs = 4–5 | luster = Vitreous | streak = | diaphaneity = Transparent | gravity = 2.77 | density = | polish = | opticalprop = Biaxial (+) | refractive = nα = 1.597 - 1.603 nβ = 1.606 - 1.609 nγ = 1.618 - 1.621 | birefringence = δ = 0.021 | pleochroism = | 2V = Measured from 74° to 78° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }} Scawtite is a hydrous calcium silicate mineral with carbonate, formula: Ca7(Si3O9)2CO3·2H2O. It crystallizes in the monoclinic crystal system as thin plates or flat prisms.

Scawtite was first described in 1929 for an occurrence at Scawt Hill in Northern Ireland.