Opal, from the Greek, "Opallos," meaning 'to see a change (of colour),' is a formation of non-crystalline silica gel. Millions of years ago, this gel seeped into crevices and cracks in the 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 opals.

The Opal is set apart from other gemstones, because of its characteristic appearance, displaying sparkling prismatic colours which change and flash as you turn the stone in your hand. No two opals are exactly alike!

In 1963 it was discovered that opal is composed of minute particles of silica in closely packed spherical arrangements. In high quality opal, the larger spheres are packed together in a remarkably regular pattern, which results in a regular three dimensional array of unfilled spaces, or voids, between the spheres. Light passing through the transparent spheres is scattered by the array of voids and diffraction splits white light into its various colours at different angles. Thus we can see the amazing play of colour and light in a precious opal. The size of spheres is less than 1/1000mm - the larger spheres provide the red fire, the smaller the green to violet.