To understand how Opal is formed first we have to look at how a rock is made. The sediment is under such high pressure that it forms a solid mass and becomes, quite literally, a ‘rock’. Silica, which is carried by water, gets left behind in any spaces or cavities, the water evaporates, and we are left with rock and silica, which equals opal. It isn’t always rock that becomes opalised. Wood and bone can undergo a similar process, and as the organic matter decomposes, the opal takes its place. There are some very beautiful specimens of shells and fossils which have become opal.

When opal is formed, deep under the earth, the silica which is deposited as the water evaporates is in actuality microscopic spheres. Any spheres, when packed together are going to leave spaces between them. It is the gaps that create the colour. Hold an opal in the sunlight for the best play of colour. The light bends between the spheres and is diffracted, which splits white light into the colours of the rainbow. We all recall our childhood schooling where they seemed to think that teaching us how to remember the colours of the rainbow was important. ROYWBIV. People remember this in variou...

Mac will be heading back out to the opal fields in mid July 2010. He plans at this stage to visit Koroit, Yowah and Lightning Ridge, with the small task of moving rather heavy mining equipment. His expedition to Koroit in the last few years proved rather difficult and he has made the tough decision to leave the mining to miners and to stick to the cutting and setting of his passion. This doesn’t mean that he doesn’t have a love for the outback and will quite happily spend a day dibbling his fingers in opal, be it rough or cut, he really doesn’t mind. With his artistic eye, he can turn what ...