White Topaz

White Topaz: Hydrous Aluminium Fluorosilicate, AL2[(f,OH)2|SiO4] ; Crystal System: Orthorhombic; name derived from Sanskrit tapas meaning fire ; Relative Density: 3.49-3.57; Hardness:8; Cleavage: eminent along base; Lustre: vitreous; Refractive Index: 1.606-1.638; Birefringence:0.01; Dispersion: weak; Pleochroism:distinct.

Occasionally found in jewellery eminating from the far East and easily distinguished again by refractometer. Visually there is much less brilliance and fire than diamond. Doubly refracting, topaz is separated from diamond by rotating it between crossed nicols in a polariscope.

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