Ruby

Rubies are very hard gemstones with only diamonds and moissanite (silicon carbide) being harder. It is a red to pink coloured gem, created by the mineral corundum, otherwise known as aluminium oxide. Its name is derived from the Latin word for red, 'ruber.' Other varieties of corundum that are considered to be of gem quality are known as sapphires.

Ruby has a variety of values, depending on it colour. The most valuable is what collectors call 'blood red.' A ruby of a clear blood red colour is then checked for its cut and weight (carat) when its value is being determined. Another important factor is its imperfection. This means it should have a needle like titanium dioxide (rutile) inclusion present. If this is not visible it is a sign the ruby may have been artificially manufactured. All natural rubies have imperfections. This may also include colour imperfections, as synthetic rubies, made in a laboratory, are always perfect in every manner. Most natural rough stone rubies are treated in some manner these days before being marketed. This usually involves heat treatment, however, when untreated in any way whatsoever and their quality is still quite good, they can retain considerable value.

Some rubies display a three point, or six point, star known as an asterism. When this star is present the ruby is cut into cabochions, as opposed to being faceted in the usual fashion, as by being cut in this way the star effect is better enhanced. This type of ruby can not be artificially created in a laboratory as its star effect comes from it reflecting light off the rutile inclusion in a particular way. One reason why inclusions increase the value of natural rubies as against artificially manufactured stones. Another very rare inclusion creates a 'cat's eye' effect otherwise known as a chatoyancy.

The first synthetic ruby was made in 1837 by fusing potash alum at a very high temperature with a trace of chromium as a pigment. In 1847 a white sapphire was artificially created by fusing alumina in boric acid and in 1877 crystal corundum was created from which small stones were able to be cut. In 1903 it was announced synthetic rubies could be created on a commercial scale and by 1910 a 30 furnace production plant was established producing 1,000 kilograms of synthetic gemstones a year.

Rubies mined in Burma became famous as pigeon blood rubies. These specific rubies were set in gold to enhance their visual effect. The purplish red ruby set in yellow was especially effective as the yellow of the gold neutralised the blue in the stone giving it a pure red appearance.

Ruby and sapphire finds have occurred in all states on the Australian eastern seaboard although there are only a few commercial mines operating. These mining operations are currently restricted to New South Wales and the Northern Territory. There is a ruby mine in the MacDonnell Ranges of the Northern Territory known as the Ruby Mining Company. In New South Wales rubies are mined by the Gloucester Company at Barrington Tops and Bald Hill Alluvials, Tumbarumba, Selwyn Company. Sapphire is mined on a commercial basis in Queensland at Lava Plains and Anakie.