Opal

Opal
Opal

Opal was the last of the gemstones to be successfully synthesized. The replication of its complex make-up of multi-sized microscopic silica spheres bonded together with hydrous silica gel drove many researchers insane. The silica gel accounts for approximately fifteen percent of the stone’s weight and over half of that is water. For it to be considered precious, hence valuable, the spheres must range in size to reflect the visible spectrum. Therefore the smallest spheres reflect red, and the largest, violet. If the spheres are over or under this size, it’s still opal, it’s just opal rock (also called “potch”). Precious opal is generally found in thin layers or seams contained within basalt or iron stone or limestone or pretty well anything that had fissures where the water could accumulate. Opal is named by the colour of the background rock in which it forms. So black opal can be anywhere from grey, to a true black, and jelly opal can be water-clear or tinted in a variety of light tones.

Opal owners must treat their stones like the most sensitive skin on a baby’s body. Avoid exposing it to any chemicals, including cosmetics. Extreme heat or cold will shatter the stone as will very dry environments. Many owners of extremely beautiful opals have put them into humidity-controlled bank vaults and returned to a useless piece of rock. If your stone is your best friend, feel free to shower with it; it loves and needs a good drink regularly. You can tell when it’s happy because its colours are revived. Just be cautious of hitting it on hard surfaces as opal is relatively brittle. Opal is the birthstone for all the lucky people born in October.

A fine opal can exhibit either an intense single colour or a play of multiple colours. What one person finds extremely attractive, another person is not interested in at all. Unlike pearls, they’re a very personal stone. Different kinds of lights will enhance different colours within the stone. So when purchasing an opal, be sure that they, like we, have a daylight source.

Australian Opal

Australia as of the 19th century has become the major opal source for the world. Ancient European mines have been depleted for centuries. And the abrupt arrival of the Australian material caused everybody to disbelieve it was actually opal. It was just too big, too beautiful and too plentiful. Australian opal is found in several different locations.

Almost all of the white opal comes from Coober Pedy which is aboriginal for “white man’s hole in the ground”. This area is very arid, sparsely populated, and still has the character of the American wild west. Because of the arid heat, most of the miners live in their mines as they tunnel through the soft bedrock following the seams of colour. Most of the milky white stones found in the average jewellery store with little points or minor flashes of colour are from Coober Pedy. But Coober Pedy is also capable of producing stones of profound colour and beauty. Unfortunately, these are really expensive.

Lighting Ridge is the other extreme for opals from Australia and it consistently produces the highest quality of black and crystal opal since the early 1900’s. The rock here is very hard and standard mining procedures are used. “Black” is actually a misnomer as “black” includes many shades of grey. “Crystal” is also variable from water-clear to milky tinted shades. Lighting Ridge opals are much more robust and can take much more abuse without damage. Although “black” opals generally have blue and green “fire”, there are multi-coloured stones produced from this area. They are very, very expensive.

Andamooka is a medium production field but it has a unique characteristic in that many of the fossilized bones and plants of previous eras are found here. It was here that the three meter long, 120 million years old, opalized fossil plesiosaur was found. As well, there is a myriad of seed pods, bones and shells that are all opalized. A truly unique archeological delight!

Mintabie, White Cliffs, and the Queensland Fields are other producers of various kinds of opal but production is very inconsistent.

Mexican Opal

The major source for opal in Mexico is Querataro province. Fire opal from this region ranges from a clear jelly through the yellows and reds into a deep, dark ruby red. The Mexican fire opal is primarily found in seams within rhyolite. This is the only variety of opal which is faceted and generally it is a non-precious opal, meaning there is no play of colours within the opal (although value has been added to the material by faceting). The normal shape for an opal is a cabochon which is similar to a soup bowl turned upside down (smooth dome top, flat bottom). Fire opals are extremely sensitive to moisture loss and temperature shock.

Ethiopian Opal

We have , in stock, many Opals of all shapes, sizes and values. We have the set, unset and as raw material. If you like Opal please come in and ask to see some. It will change your mind when you see how varied this stone can be.

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