Australian Sapphire: Gemstone Information
Australian Sapphires were found in the alluvium of streams on Frazer’s Creek near the town of Inverell in the New England area and the name Sapphire was taken up by the settlement which grew up. Production tailed off in the 1930s as more stones were coming from deposits in South-east Asia. As prices for Australian sapphires improved the search for and marketing of New South Wales material took on new life. Deposits in the New England district which at first were accessible to the solitary miner produced less and mechanized operations took over. The export of geuda from Sri Lanka to Thailand for treatment also made it more difficult for the Australian sapphire industry.
Mumme gives considerable detail of the New England sapphire production and also describes the crystals. In the alluvial deposits crystals are found as fragments with the common form of tapering hexagonal prisms though some well-rounded crystals also occur. Colours are dark blue or dark green with intermediate shades of either colour; yellow crystals are rare. The dark blue colour is seen parallel to the ordinary ray and colour zoning is pronounced. Hollow cavities, rutile needles and cavities are common. The Anakie sapphire deposit in central Queensland was proclaimed in1902 as a recognized commericial field. While corundum fragments have
been found in the basalt, crystals are recovered from alluvial sources (‘wash’). The proportion of gem to non-gem-quality material is low but as well as blue and green which predominate, a wide range of colours has been found, including golden yellow and star stones. The very occasional ruby and colour change crystal has been reported. The name Rubyvale does not appear to indicate a plentiful supply of ruby. The official geological report on the Anakie field can be found in Publications of the Geological Survey of Queensland, 172, 1902. In general, the Australian sapphire is either dark or heavily included, but often both. Nonetheless many stones may be considered the best of their colour, this applying in particular to green specimens. Heating can improve many examples. Green and yellow stones, in particular, show a clear absorption spectrum though the iron content inhibits the yellow stones from fluorescing (Sri Lankan yellow stones usually show a distinct fluorescence but faint absorption spectrum). In 1978 flattish ruby crystals, rubies of poor cabochon grade, were recovered from a shallow subsurface deposit on the Harts Range, northeast of Alice Springs, Northern territory.