About Opals

The opal has been cloaked in magic and mystery for centuries. It is set apart from other gemstones because of its characteristic appearance and vibrant colours, which change and flash as you turn the gem in your hand. No two opals are alike. The word 'opal' comes from the Greek word opallos, meaning "to see changes of colour", although the Romans are said to have based their name opalus on the Sanskrit word for precious stone, upala.

Opal is classified as a precious gemstone. It is a formation of non-crystalline silica gel. Millions of years ago, this silica gel seeped into crevices and cracks of the earth's sedimentary strata. Through eons of time and through nature's heating and moulding processes, the gel hardened and can today be found in the form of brilliant opal.

Opal contains about six to 10 per cent water and consists of small silica spheres arranged in a regular pattern. Colour is caused by the regular array of silica spheres diffracting white light, and breaking it up into the colours of the spectrum. The diameter and spacing of the spheres controls the colour range. In potch opal, which displays no colour, the silica spheres may be absent or too small or arranged irregularly to produce colour.

Generally, opal measures 5.5 to 6.5 on MOH's hardness scale with diamonds measuring 9 to 10 and pearls 4 to 5. Opal is recognised as the birthstone for October.