Thaumasite
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Thaumasite is a calcium silicate mineral, containing Si atoms in unusual octahedral configuration, with chemical formula Ca₃Si(OH)₆·12H₂O, also sometimes more simply written as CaSiO₃·CaCO₃·CaSO₄·15H₂O.
It occurs as colorless to white prismatic... Wikipedia
Crystal class: Pyramidal (6); H-M symbol: (6)
Crystal habit: Prismatic, fibrous, massive, radial
Crystal system: Hexagonal
Formula mass: 622.62 g/mol
Mohs scale hardness: 3.5
Optical properties: Uniaxial (−)
Space group: P63