Opals Part 1

A lot of our customers love Opals because of their mystery and the way they change in the light. In particular they are very popular for earrings and pendants.

Opal’s internal structure makes it diffract light; depending on the conditions in which it is formed it can take on many colours. They range from clear through white, grey, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. The reds and black tones are the rarest type whereas white and greens are the most common. The stone also varies in density from opaque to semi transparent. The colours can be enhanced by using basalt.

There’s lots of different names for the different types of Opal, Dark or Black Opal, White or Light, Milk or Crystal, Boulder, Matrix, Yowah Nuts from Queensland and also Mexican and fire opal. The variations are practically unlimited.

They all show in their own special way that unique play of colours – except for Fire Opal, which is due to its transparency. If they are lacking the typical play of colours, they are simply named “Common Opal”. Ordinarily, if precious, they show a variable interplay of internal colours and does have an internal structure.

Keeping them safe

The hardness of opal is 5.5 to 6.5. therefore they appreciate a protective setting. In earlier days Opal’s sensitive surface was often oiled, but today also sealing them with colourless artificial resin has become quite popular.

Opal doublets, often used in jewellery, are thin slices of precious opal glued onto a base material. Such gems are considerably cheaper than solid opals, yet provide the same play of colour. Opal doublets are sometimes coated with a thin layer or dome of clear Quartz to make them more resistant to scratches (since Opal is a relatively soft gem). These are sometimes called triplets.

Due to the differing percentage of water, this gemstone may easily become brittle. They always contain water – usually between 2 and 6 per cent, but sometimes even more. Thus if stored too dry or exposed to heat over a longer period of time, will show fissures and the play of colour will become paler. Therefore, they should be worn as often as possible, then the gemstone will receive the needed humidity from the air and from your skin while it’s worn.

Best cuts

In order to bring out the best play of colour, the stones are cut and polished to round or oval cabochons, or any other softly domed shape depending on the raw material. Only the best quality, however, are suited to faceting. The cutter will first of all carefully remove any impurities using a diamond cutting wheel, before working out the rough basic shape. This comes the fine cutting, the finishing with sandpaper and then the final polishing with a wet leather wheel.

In my next article I will discuss the origin and history of the Opal.