Minerals and Metals in Ancient India v2.c43.s3.t6.2

v2.c43.s3.t6.2

Zircon (hardness 7-1/2) is the orthosilicate of zirconium, ZrSiO₄. Pure zircon is colourless, little iron giving it a colour which is brownish shade of orange, a mixture of red and yellow. Strongly reddish-yellow variety of zircon is known as hyacinth; this contains more iron in the ferric form. Pale straw-yellow or colourless zircon known as jargon contains iron in the ferrous form. Inter-conversion between hyacinth and jargon is possible by heating under oxidising or reducing atmosphere.