by Manisha G

fluorspar-gemstoneChemical composition: Calcium Fluoride

Crystal characteristics: Cubic system. Usually occurs in cubes.

Colour: Violet blue, purple, green yellow, pink, brown, blue, etc. Rarely colourless. Massive purple and whitish banded variety known as “Blue John”. Often parti coloured fluorspar is common.

Physical properties:

Hardness – 4, too soft to retain polish. S.G. – 3.18, R.I. – 1.434 (both constant) single refracting low dispersion. Easy but rather imperfect octahedral cleavage.

Other Important points: Most specimens of fluorspar show a vivid violet blue fluorescence under ultra violet light. This may even be apparent to day-light. The mineral, indeed, gave the name to the effect. Fluorspar often provides beautifully crystallized transparent mineral specimens, and only its softness prevents it from being more used for ornaments.

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