Scawtite

Scawtite
Scawtite.jpg
General
CategorySilicate mineral
Formula
(repeating unit)
Ca7(Si3O9)2CO3·2H2O
Strunz classification9.CK.15
Dana classification64.2.1.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 10.12 Å, b = 15.18 Å
c = 6.62 Å; β = 100.55°; Z = 2
Identification
ColorColorless
Crystal habitPlaty - micaceous, parallel to radiating clusters
CleavagePerfect on {001}, poor on {010}
Mohs scale hardness4–5
LusterVitreous
DiaphaneityTransparent
Specific gravity2.77
Optical propertiesBiaxial (+)
Refractive indexnα = 1.597 - 1.603 nβ = 1.606 - 1.609 nγ = 1.618 - 1.621
Birefringenceδ = 0.021
2V angleMeasured 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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