Abstract

Carletonite, KNa4Ca4Si8O18(CO3)·(F,OH)·H2O, occurs in thermally metamorphosed inclusions in the nepheline syenite at Mount St. Hilaire, Quebec. It is associated mainly with pectolite. albite, arfvedsonite, calcite, fluorite, and apophyllite.

The mineral is tetragonal, P4/mbm, with a = 13.178±.003 Å, c = 16.695±.004 Å, c/a = 1.2669. The strongest X-ray powder diffraction lines and their relative intensities (visual), are: 8.353(100), 4.171(100), 4.053(50), 2.903(90), 2.384(60). Z = 4

Carletonite is pink to pale blue, with vitreous to pearly luster. H = 4-4½ on {001}. Density (meas.) = 2.45 g/cm3, (calc.) =2.426 g/cm3. Cleavage {001} perfect, {110} good, fracture conchoidal. Optically uniaxial ( — ), ω = 1.521 α0.001, ϵ = 1.517α0.001, in Na light, for pink and blue varieties. The blue variety is weakly pleochroic with O = very pale blue and E = very pale pinkish brown.

Analyses of pink and blue varieties gave, respectively, SiO2 44.9, 44.7, TiO2 tr., tr., Al2O3 0.5, 0.6, total Fe n.d., n.d., MgO 0.C9, C.13, CaO 19.92, 19.97, Na20 10.23, 10.64, K20 3.28, 3.31, CO2 —, 15.2, F 0.70, 0.73, H2O 0.70, 0.63, H2O+ —, 3.51, LOI 19.92, —, sum 100.24,99.42, - (O = F2) 0.29,0.30 = 99.95,99.12%.

DTA shows endothermic peaks at 300°C (vw), 692°C (vs), and 915°C (vw), and an exothermic peak at 736°C (w). TGA shows 0.7% weight loss below 430°C and 17.3% above 430°C with major loss between 650° and 750°C. Infrared spectrum and its interpretation are given.

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