The opal is a non-crystalline mineral of hydrated silica occasionally displaying a beautiful play of colour, hence its value as a gem stone. The precious or “noble” opal, as the real gem is called, is, however, but one variety, and is only found in a few places.

The finest opals come from Hungary, near the village of Vorosvagas or Czerwenitza. For centuries, in this place commerce in opals has been carried on, one uncut specimen preserved in the Imperial Museum in Vienna weighing about 3000 carats. Other places where the ” precious ” opal is found, are the Mexican state of Queretaro—where it occurs in a porphyrinic rock at Esperanza; at Gracias a Dios in Honduras, in Queens¬land near the Barcoo river, and in New South Wales, Yungnulgra county.

The opal was valued by the Romans next to the emerald, and a rich Roman senator, Nonius, was exiled by Mark Antony so that the latter might seize the former’s magnificent opal, which was as large as a hazel nut. Because of its marvellous colouring, the opal has always been surrounded by superstition. By some people it is regarded as a lucky stone, by others as unlucky.