The Chemistry Properties and Tests of Precious Stones (Esprios Classics)

What constitutes a precious stone is the question which at the onset rises in the mind and this question simple as it seems is one by no means easy to answer since what may be considered precious at one time may cease to be so at another.There are however certain minerals which possess distinctive features in their qualities of hardness colour transparency refractability or double refractability to light-beams which qualities place them in an entirely different class to the minerals of a metallic nature. These particular and non-metallic minerals therefore because of their comparative rarity rise pre-eminently above other minerals and become actually precious.