The Opalstop

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Information about Opal

Chiseling out from the opal seam.Opal is primarily made up from a variety of natural silica found in the earth. Over very long periods of time the silica is mixed with water (rain) and is deposited in cracks and holes in the earth, hardens and becomes opal.

The worldwide opal industry relies heavily on Australia for it's supply. A massive 95% of opal used for jewellery purposes is found in Australia. A small number of other countries including Mexico, brazil and the USA do produce some opal but it is inferior and simply does not have the appeal and instant recognition that Australian opal holds.

Where opal is found.

Map of opal mining fields in Australia - click to open a details map in a new windowThere are three main opal mining regions in Australia with each producing a different variety of opal.

White Opal.

White Opal is sometimes referred to as "milk" opal and is found in and around the towns of Coober Pedy , Mintabie and Andamooka in South Australia. 

Black Opal. 

The most famous and recognisable of all opal is found around the town of Lightning Ridge in the state of New South Wales.

Boulder Opal.

Boulder Opal can be found in pockets in central Queensland over a vast area. Some of the more famous areas are Quilpie, "Winton" and "Opalton".

Click this link for a detailed Map of opal fields and deposits around Lightning Ridge [this link will open a new window]

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Mining Opal.

The opal shaft.The 2 main methods for mining opal are the open-cut method and the more traditional shaft method which is still mostly used for the mining of black opal.

A large drill is used to "sink" a shaft to a certain depth allowing miners to descend the shaft and using implements such as picks, shovels, jackhammers etc. they can then branch out in different directions looking for the "seam" or "nobby" patch of opal dirt that may contain the precious gem.

Opal hoists perched over their minesThe opal dirt is then hoisted to the surface and water is used to wash this dirt and unearth what treasures may be there.

As you can imagine this work is very hard and dangerous.

The open-cut method is done by the use of heavy machinery to remove large amounts of opal dirt from closer to the surface for inspection.

This method is more expensive and is mostly used to search for boulder opal in central queensland.

Cutting and polishing the stones.OPALSTOP have employed this method on several occassions to search for precious black opal in NSW but our main sources of opal are found by the shaft mining method.

 Cutting and Polishing

Once the opals are mined they will be cut and polished by experts to remove any remaining dirt and opal potch that is still attached and reveal the true colours and patterns that exist in each individual stone. Almost all opals are cut in the cabochon form and due to the nature of opal they generally will be cut in freeform shape so as to maximise the potential in size and colours that may be present in the stone.

Visit the Opalstop Picture Gallery for a pictorial record of the day to day workings of the opalstop.

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Caring for your opals.

In 1812 a German mineralogist named Frederich Moh developed what is called the Moh's scale. It has a range of 1 to 10 and gives an indication of the hardness of a substance. Diamond is rated as a 10, and talc as a 1. Opal is rated about 6.5 on this scale indicating that it is not one of the hardest gem stones. Therefore it is wise to remove your opal jewellery(especially rings) when doing chores in which you may knock or scratch your opal. Also, opals should be removed when there is a possibility of them being submerged in water for long periods of time. This is especially important when it comes to doublet and triplet opals as glue is used to attach the opal pieces to their backings and tops. When over exposed to water it will penetrate under the pieces and the glue will lift giving the opal a smokey look. Please note this will only happen due to over exposure to water.

When cleaning solid opals, never use any chemicals or industrial cleaners. Simply use a mild detergent and with some warm water give the opal a wipe with a soft cloth. The same applies to doublet and triplet opals but limit the use of water by just dampening the cloth.

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Opal Terminology

Close up of some rough.BLACK OPAL - The most rare and valuable type of opal. Black opal has a dark underlying body colour, which gives greater intensity to the opal stone's colour. The word black doesn't refer to the face of the opal. Black opal comes in every colour of the rainbow.

CRYSTAL OPAL - Opal that is transparant or translucent. Crystal opal can be extremely beautiful. Although Lightning ridge is most famous for black opal, it also produces exquisite light and crystal opal.

BOULDER OPAL - Boulder opal is only found and mined in Queensland. The gem is found in a matrix or surrounding rock called ironstone or dark brown sandstone.

DOUBLET - A doublet is made by fusing a dark backing, (which can be natural black potch as used in all our opalstop doublets) to the back of the gem opal, producing a double layered gem with an appearance similar to black opal.

TRIPLET - A triplet is similar to a doublet except that the slice of gem opal is very thin, and a third layer, usually a layer of tanspaent material e.g. a domed piece of hard plastic or quartz crystal is added to the top of the gem.

POTCH - A form of non-precious opal that doesn't contain gem colour. Potch is usually black, grey, white or amber coloured.

NOBBY - A naturally lump-shaped piece of opal. The nobby form of opal is only found at Lightning Ridge.

SEAM - A horizontal layer of opal in the ground. Opal is found in a seam as well as a nobby formation in the lightning ridge area.

OPAL ROUGH - Opal that hasn't yet been touched by cutting equipment.

OPAL CUTTER - A skilled person who cuts and then polishes rough opal into the finished gemstone. 

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