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194
PRECIOUS STONES.
In Australia, New South Wales, in the New England dis­trict, in Diamond localities. Here the green Corundum, Oriental Emerald, is relatively common—as a rule it is one of the rarest colours. The Sapphires are usually of a very deep blue. In Bohemia Sapphire has been found with Zircon and Garnet.
What has been said of the cutting of the Euby applies to Sapphire also. The fact that the colour is of a richer hue when viewed along the principal axis of the mineral should guide the lapidary in cutting the stone. Sapphires are particularly prone to be patchy in colour, and bad parts may have to be removed by slitting before grinding com­mences. Sapphires usually show a change of colour in artificial light; some few specimens change to violet, thus, and they are highly prized. Most Sapphires have their colour destroyed by heat, some very much more easily than others.
The value of Sapphire of good quality, and in carat size, is about two-fifths that of Euby. Moreover, since Sapphires of large size are more plentiful than in the case of the Ruby, there is not the same rapid increase with size. Small stones may be said to be very much the same in value as Diamonds, and larger stones only increase in about direct proportion to their weight.
The minerals most likely to be substituted for Sapphires are blue Iolite (Saphir d'Eau), blue Tourmaline (Indicolite), and Cyanite (the Sapphire of de Saussure). Less likely to be found under this name are blue Topaz, blue Spinel, blue Fluor Spar, blue Quartz, Aquamarine, and Hauyne. Blue Diamond may resemble it very closely in colour, but no attempted substitution is likely to be found in this case.