Opal is a naturally-occurring amorphous solid known for its flashes of fire color. An amorphous solid is a material that, unlike crystal, is not organised in a regular lattice pattern. This makes for some unusual interactions with light, and is explicable for opal’s rainbow colours.
However, just because opal is classified as amorphous is not to say that its atoms are arranged without order. Chemists have discovered a clear sphere structure in opal, which has led to them copying it in 1974. Synthetic opal is often named Gilson opal, after Pierre Gilson, the man who invented it (along with a number of other synthetic minerals: coral, emerald, lapis lazuli, etc.). If you’re looking for someone to blame for having paid over the odds for a synthetic substance, by the way, Pierre Gilson is the man you’re looking for.
Originally synthesised in Switzerland, Glison opal is now primarily synthesised in Japan (by Kyocera and Inamori, for example). It differs from natural opal inasmuch as it is much more regular. Synthetic opal, though less desirable than organic opal in the eyes of most lapidaries, is not to be confused with imitation opal, which, unlike pure synthetic opal, is tinctured with minerals not found in actual opal. The term “Gilson opal” is usually used to refer to imitation opal, opals which are not only lab-created but contain minerals not found in actual opal (minerals such as plastic in Slocum stone, for example).
If you ever find yourself in the market for opals, you’d be well advised to bring a loupe along with you. Under a high magnification (of around sixty), it’s clear to tell by the regularity and columnar nature of the patterns that the opal is synthetic. Even to the naked eye, the columnar nature of the opal is plainly visible. With the help of a loupe you’ll be able to discern a so-called ‘lizard skin’ effect in the patches of colour. This crumbly surface is the most common “tell-tale” of synthetic opal.
Synthetic opals are said to fluoresce a green colour under UV light. Along with the loupe, you’d be well advised to take a UV torch along with you to the flea market (or wherever you go to get your opals). If it fluoresces, it’s synthetic; if not, it’s natural.
Synthetic opal comes in two main kinds: white opal and black opal. The white opal is generally more expensive than the black, largely because the white is more natural-looking than the black.
SHOP FOR OPAL
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