Scawtite

Scawtite
General
Category Silicate mineral
Formula
(repeating unit)
Ca7(Si3O9)2CO3·2H2O
Strunz classification 9.CK.15
Dana classification 64.2.1.1
Crystal system Monoclinic
Unit cell a = 10.12 Å, b = 15.18 Å
c = 6.62 Å; β = 100.55°; Z = 2
Identification
Color Colorless
Crystal habit Platy - micaceous, parallel to radiating clusters
Crystal symmetry Monoclinic - prismatic
H-M symbol (2/m)
Space group: C 2/m
Cleavage Perfect on {001}, poor on {010}
Mohs scale hardness 4–5
Luster Vitreous
Diaphaneity Transparent
Specific gravity 2.77
Optical properties Biaxial (+)
Refractive index nα = 1.597 - 1.603 nβ = 1.606 - 1.609 nγ = 1.618 - 1.621
Birefringence δ = 0.021
2V angle Measured from 74° to 78°
References [1][2][3]

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.[2]

Scawtite was first described in 1929 for an occurrence at Scawt Hill in Northern Ireland.[2]

Scawtite occurs as in skarns and hydrothermal veins in limestone. Associated minerals include melilite, spurrite, tobermorite, thomsonite, larnite, grossular, bultfonteinite, calcite, analcime, foshagite and hillebrandite.[1]

References

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