CHOOSING THE RIGHT OPAL When you are choosing your opal it is VITAL that you know how the opal will be worn, as some opal will look brighter when viewed vertically whereas others will show more colour when viewed horizontally. SOLID OPAL Opal that has been mined and is presented either in its naturally occurring state or after being cut and polished. It has not been chemicalIy treated and has no other materials cemented to it. These solid opals include: BLACK OPAL Opal with black or dark naturally occurring base and background colour. CRYSTAL OPAL Opal which is predominantly translucent when held up to the light but showing strong colour refractively. WHITE OPAL A predominantly white or opaque background colour in refractive plane. BOULDER OPAL Opal that has formed naturally on ironstone or "boulder" which is cut to form that host rock. MATRIX OPAL Host rock that is impregnated with natural opal which cannot be readily separated from that host rock. Non-solid opals include: LAMINATED OPAL A thin layer of solid opal that is fixed to a base of opaque material, and also has a clear top. DOUBLET A veneer of precious opal is cemented to a dark or black base to provide sufficient depth to the stone to enable it to be set in jewellery and enhance its natural colour. TRIPLET To protect the opal from abrasion, a slice of quartz may be used to cap a veneer of opal that has been cemented to a base, producing a three tiered gemstone. This type of gem can display brilliant colours because of the enhanced appearance of the opal.