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.
Mining opal today still has all the aspects of a Wild West town from 1800s United States. Most of the Australian opal is found in the country’s remote deserts, which has a “blistering, almost unliveable climate.” Indeed, many opal miners dig their living quarters underground, in an attempt to stay cool.
Lightning Ridge, on the other hand, is significantly cooler, and there’;s enough moisture to support tree growth (albeit, scrub trees).
However, there’s till not a lot of water, so what the miners do is form “wash cooperatives.” Since it’s easier to find opal when its wet, all the dirt and gravel dug out of a mine is driven to one od many dam sites. There, the material is dumped into an agitator. The dirt is tumbled around for 4 to 5 hours, sprayrf with water, so that most of the gravel pours out of the sides of the agitator. The rest of the material slides down into an area where the miners look it over, inspecting each piece by hand.
The residue, the grit and gravel, is dumped into “mullock heaps” near the top of the dam.
Anthropologist Louis Leakey discovered the earliest known opal artifacts in a cave in Kenya. They have been dated to about 4000 B.C. The current theory is that they were mined in what is now Ethiopia, and perhaps sold or traded to people who then returned to what is now Kenya.
Wealthy citizens in ancient Rome loved to acquire opal – it wa srarer than pearls and diamonds. The Roman writer Pliny shares tales of opal coveted by Marc Antony for Cleopatra, in 50 BC.
No one issure where this opal acquired by Roman citizens came from. Pliny believed it came from India, however experts believed that it was mines in what is now Hungary that supplied these gems.
In the Middle Ages, Hungary mined opal which it supplied to Europe and the Middle East. The civilizations of Mexico, Peru and Honduras supplied their own gemstone wants from their opal mines.
Conquistadors returning to Spain brought opal with them in the early 16th century.
However, since the late 1800s, it has been Australia that has dominated the opal market. Austtralia produces 90% of the world’s opal. About 20 other countries supply opal as well – Canada, Ethiopia, Guatemala, Indonesia, New Zealand, Peru, Poland, and Zambia. Gem opal typically comes from the USA, Brazil and Mexico.
