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unmounted 'opalus'
'opalus' pendants
opal simulant 'opalus'

Opal Simulants

Opal simulants have come in a variety of forms. They can be made by forming colourless non-siliceous particles into microspheres of the correct size and allowing them to settle, when diffraction colours may be obtained. A simulant using a synthetic resin for this purpose has been made in Japan. It has the appearance of a light coloured Coober Pedy opal, and is very deceptive. If unmounted, however, it is 'given away' by its low density; it feels light in weight when held in the hand.

Other techniques have been used in attempts to simulate the appearance of opal, most with limited effect. Simple methods such as mounting crinkled thin foils between a base and a transparent cabochon have been used. Another type ('Slocum stone') footnote incorporates thin reflective film in a glass. These materials have a transparent appearance, and the colours are largely produced by light interference.

Through a magnifying glass the thin individual flakes of metal, which gives the 'Slocum stone' its vibrant colours, seem to correspond with chipboard-like flakes of metal, those which have been split or broken into smaller pieces during the manufacturing process. The appearance of being broken into pieces is especially noticeable when light passes through the stone.

As well as these metallic flakes, inclusions of gas bubbles and 'schlieren' are often found, which, by their presence, help to identify the material.

Gerald Pauley has patented a new type of simulated opal called 'Opalus' using computer graphics and specially designed holograms. To create the textures and patterns, photographs were taken of a large number of opal patterns, colours and textures. These were then scanned into a computer and amalgamated into complete random patterns from which simulants where no two were the same could be made. In the first instance the colour patterns generated from the computer were representative of the base colour of the opal. The hologram was then applied to give the appearance of changing colours. The simulated opal is made in high quality acrylic and can be mass produced in any shape or size, or can be made to replicate carvings. In addition, black opals can be simulated using this process.

A second Pauley process creates a simulated opal using holograms and colour interference layers which allow the colours to appear through the surface of the product. An unlimited pattern range simulating those of the natural opal can be created.