An opal is hardened silica gel usually containing 5-10% of water, so unlike many gemstones it is non-crystalline. Opals usually have a lovely coloured iridescence of rainbow like colours on a white background, although some are on a black background. These colours are created by a regular arrangement of tiny silica spheres which refract the light, the larger the sphere, the greater the range of colours.
It is found in cavities of sedimentary rock or veins in rocks, forming stalagmites or stalactites replacing organic material in fossil wood, shell or bone. Since the 19th century Australia has been the major source of opal, although some are found in the USA, Czech Republic and South Africa.
In ancient history the Romans called in opalus, that was synonymous with ‘precious stone’, symbolising love and hope. In 75AD Roman scholar Pliny observed that some opals carry within them the deepest and richest colours of the finest painters. Indeed others felt that the stone had all the colours of gemstones, from greens of emeralds to pink red of rubies, to deep blues of sapphires.
Greeks believed that opals guarded the wearer from disease, and in Europe the gem has long been regarded as a symbol of hope, purity and truth.
It is the birthstone for October and opals have been thought to be unlucky by some. However, that is a myth as it was portrayed as such by Sir Walter Scott in his novel Anne of Geierstein. In fact, the opposite is true, opals have throughout history been regarded as the luckiest of stones, and was believed at one time to be an actual preserver of life.
Opals do come in other colours, one being the orange red- Fire Opal. This does not look like an opal in any way, and are mined in Mexico. Aztecs loved this stone and it was believed it was created in the water of paradise. It is extracted in open mines in the Mexican highlands, many with their extinct volcanoes the work giving rise to impressive canyons with walls up to 60 metres high. It is regarded as their national gemstone.
There are many imitations, one being the opal doublet. This is where two layers are created, a black plastic backing and overlaid with a thin layer of crystal or white opal, this would then give the impression of a highly coloured gem quality opal. However, they are easy to detect if looked underneath as the black backing is clear to see.
We have many Vintage opals in our store which we welcome you to browse at Vintage Tom