According to Paul Downing, PhD, an acknowledge expert in all aspects of opal — from mining to cutting to setting into jewelry.
Most commercially set opals that you see in jewelry stores were set improperly, during Downiing’s heyday in the 1990s, and I mention his strictures here because you never know when a jeweler might not go back to the bad old ways necause it takes less time, even if the jewelery suffers.
Downing points out that opals are not too fragile to wear, if only they are set properly.
Some jewelers set opals in mounting reserved for faceted stones, like diamonds. And since opals are more fragile than diamond, they do indeed break when set in that manner.
The most fragile part of a cut opal is the bottom edge, so to prevent the gem from cracking in its setting, it should be completely surrounded by, or nestled in, metal. On no account should you purchase opal sitting up in a set of prongs, with no gold or other medal around it.
If you have precious opal atop either common opal or another substance, is it considered a doublet? No – not if they are formed naturally together.
Natural opal – natural precious opal cut to include common opal or potch in one piece
boulder opal - opal cut to include ironstone, rather than common opal or potch)
Doublet – A natural opal assembled with common opal, potch, or any other material
Triplet - the same.
Some dealers attempt to sell assembled opal and ironstone as boulder opal – don’t be fooled!
A wavy line between the two indicates a natural boulder opal. A straight line = an assembled boulder opal, i.e., a doublet.
The fields of boulder opal extend throughout most of southern Queensland, from Hubgerford to Winton. Most of the mining activity occurs around Quilpie, in the south, and Opalton, near the center of Queensland.
Boulder opal is famous for its color intensity. No othr opal type can match the size and vibrancy of the color spots that are visible when the piece is held at angles to catch the play of fire.
In adition, the three-dimensions of boulder opal make it easier for jewelry designers to do some unique things with their jewelry. Matched earrings are particularly popular. “Splits” – a boulder opal split in two so that one half is a mirror image of the other half, are as rare as matched emeralds, rubies or colored diamonds…and their prices reflect this.
Boulder opal is also renowned for its durability. Because water content of boulder opal is low, it almost never cracks or crazes as the years go by.