Sapphire and ruby are gem varieties of the same mineral, corundum. They crystallise in the trigonal system. Although both are aluminium oxide, the addition of different trace elements gives the two varieties different colours. All colours of gem corundum except red are called sapphire. Red corundum is called ruby. Ruby owes its colour to traces of chromium in its structure, while sapphires derive their colour from trace elements such as iron, titanium and nickel.
- Chemistry: Aluminium oxide
- Hardness: 9
- Refractive Index: 1.76 - 1.78
- Specific gravity: 3.90 - 4.00
- Lustre: vitreous
In Australia, sapphire is found in a number of east coast localities, from north Queensland to north-east Tasmania. The largest and most economic deposits are found in the New England area, New South Wales, around Inverell and Glen Innes, and in central Queensland, around Anakie and Rubyvale.
New South Wales
The New South Wales sapphire fields around Inverell and Glen Innes produce Australia's finest blue sapphires. A range of other colours also occurs, including green, yellow, orange and pink.
Ruby is found at various sites in New South Wales, including the Macquarie and Cudgegong Rivers, Tumbarumba and the New England area. The most significant occurrence is near Gloucester, in the drainage of the Barrington volcano. The Barrington/Gloucester area has been fossicked and mined for gold, ruby and sapphire.
Rubies and pink sapphires are occasionally found in the New England area.