Some say you have to be a bit crazy to mine opal, the heat, the flies, the isolation, but the sacrifices made can be very rewarding.
All the Australian opal fields are situated in arid inland areas of the Outback, and the opal is found at shallow depths, normally less than 30 metres, in deeply weathered rock in which there has been considerable silica movement.
What is opal?
Australian Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low
temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl and basalt. 97% of opal is produced in Australia.
Australian Opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare, whereas white and greens are the most common.
Worlds Largest
The town of Coober Pedy in South Australia is a major source of opal. The world's largest and most valuable gem opal "Olympic Australis" was found in August 1956 at the "Eight Mile" opal field in Coober Pedy. It weighs 17,000 carats (3450 grams) and is 11 inches long (280 mm), with a height of 4¾ inches (120 mm) and a width of 4½ inches (115 mm). It is valued at AUD$2,500,000
Sinking A Shaft
Although this is one of the most effective ways of finding opal, it is really hard work. The length of the shaft could be as little as three metres or as long as 20 metres. A drilling rig with a large bucket auger would save a miner several days of hard hand digging.
A variety of miner's tools are needed, including a hand windlass or motorised winch that is placed over the hole to lift dirt to the surface or by using large Vacuum machinery.
Puddling And Rumbling
This technique is used particularly at Lightning Ridge. Once the opal dirt has been transported from the shaft by trucks, puddling is performed at specially constructed dams.
A puddler is a large mesh-lined drum attached to a motor. This device rotates and turns the clay into sludge as water is pumped into the drum. The sludge escapes through the mesh. Only the hard pieces - rocks, stones and 'opal nobbies'- are captured in the mesh.
Open-cut Mining
This mining technique is created by running over a large area with a bulldozer, slicing through thin layers of sandstone until the opal level is reached. Although this method is more expensive than shaft mining, the chances of finding opal are increased because such a large area is being covered.
Noodling
In simple terms, a noodler is a person who goes over what other miners have discarded as 'dud' mullock heaps. All that is needed is a sieve and a very keen eye. An abandoned open-cut mine is another good place for a noodler, using a rake and sieve for tools.
Living Underground
Like the locals that live in the opal town of Coober Pedy South Australia, visitors can stay underground, at The Desert Cave Hotel.
Sleeping underground is a unique experience. Quiet, cool, dark and airy - the rooms are spacious with high ceilings. Most visitors say that sleeping underground gives them the best night's sleep they have ever had. It is an experience not to miss. The Desert Cave Hotel also has underground shops, a cafe, an opal interpretive centre, and an underground bar and gaming room. The hotel offers visitors the best opportunity to experience Coober Pedy 'dugout' living.
Get Rich
Tours are also available in Coober Pedy, where you will be supplied with a hard hat, torch and handpick, so you can get down and dirty, fossicking for your own fortune of opal.
TYPES OF OPAL
Agate Opal. Banded variety of Opal.
Amatite. Opal in the form of thick mounds, formed from hot silica-rich springs. See also Geyserite.
Amber Opal. Opal with a brownish to yellowish background colour, resembling Amber.
Andamooka Opal. Opal from Andamooka, South Australia.
Banded Opal. Form of common opal with colour bands. Synonym of Agate Opal.
Bandfire Opal. Precious Opal with play of colours in wavy bands.
Black Opal. Precious Opal with a black, dark blue, dark green, dark grey or similar darkly coloured background or base
colour. Black Opal is the most valuable form of Opal.
Bone Opal. Opal pseudomorph after a bone.
Boulder Opal. Precious Opal from Queensland, Australia, found in the cracks of, or as coatings on, ironstone or sandstone boulders.
Cachalong Opal. Opaque, highly porous type of Common Opal.
Cherry Opal. Orange-red to bright red variety of Mexican Fire Opal.
Chloropal. Common Opal similar to Prase Opal, but with a lighter green hue.
Chrysopal. Common Opal similar to Prase Opal, but with a golden-green colour.
Claro Opal. Transparent Precious Opal from Mexico with an intense red, green, blue, and yellow play of colour.
Common Opal. Any Opal lacking play of colour.
Contra Luz Opal. Precious Opal where the play of colour is visible only when a light source is behind the stone. Coober Pedy Opal. High quality Precious Opal from Coober Pedy, South Australia.
Crystal Opal. Transparent to translucent Precious Opal where play of colour is visible on the surface and in the interior of the stone.
Dark Opal. Synonym of Black Opal.
Diatomite. Opal replacement of microscopic shells of diatoms (type of microscopic organism) clustered together. It is white, opaque, and chalky in texture. Synonym of Tripolite, Fuller's Earth, and Diatomaceous Opal.
Ethiopian opal form welo and Gondar ,new ly discovered opal fields dierect from opal wholesalers and miners
Fire Opal. Fire Opal is incorrectly used to describe Precious Opal, or Opal with play of colour. The true definition of Fire Opal is Opal with an orange to red colour. If the Fire Opal displays play of colour, it is more correctly known as Precious Fire Opal.
Flame Opal. Precious Opal where the play of colour consists of red streaks or bands that flicker like a flame when the stone is rotated.
Flash Opal. Precious Opal with large schillers that abruptly appear and disappear as the stone is rotated.
Flashfire Opal. Synonym of Flash Opal (above)
Fossil Opal. Opal pseudomorph of organic matter such as shell, bone, and trees.
Gelite. Opal (or Chalcedony) as an accessory mineral that acts as the bonding agent of Sandstone or other cemented rock fragments.
Geyserite. Opal formed from deposition of hot water springs. Also called Perlite, Fiorite, or Geyser Opal. See also Amatite.
Gilson Opal. Synthetically produced Opal.
Girasol. Yellow or orange variety of Precious Opal in which the play of colour seems to follow the sun as the stone is rotated.
Glass Opal. Synonym of Hyalite
Gold Opal. Common Opal with a golden hue.
Harlequin Opal. Precious Opal in which the play of colour is arranged in a consistent harlequin, diamond-shaped, or rectangular-shaped pattern that is very vivid. Harlequin Opal is one of the rarest and most prized forms of Opal.
Honey Opal. Transparent to translucent Opal with an orange to orange-brown, honey-coloured background. It may or may not display play of colour.
Hungarian Opal. Any Precious Opal from Europe. However, nowadays this term often refers to any White Opal, regardless of where it was found.
Hyacinth Opal. Synonym of Girasol
Hyalite. Colourless, misty-blue, or sky-blue transparent variety of Common Opal. Usually forms botryoidal masses as well as strange and unusual forms. All Hyalite fluoresces green.
Hydrophane. White, opaque, highly porous Opal, that, when placed in water, allows the water to seep into it. This causes the stone to become transparent and almost invisible while in the water.
Iridot. Old name given to Opal for a short period of time when Opal had a reputation of causing bad luck.
Isopyre. Impure, dark red form of Opal. Isopyre was once thought to be a separate mineral.
Jasper Opal. Brecciated Jasper in which the cementing material is Opal.
Jelly Opal. A transparent Precious Opal with a gelatinous appearance and a bluish sheen. Jelly Opal may also refer to a colourless, transparent Common Opal.
Lechosos Opal. Precious Opal with a milky-white background colour displaying a strong play of colour. May also refer to Opal with a strong green schiller.
Lemon Opal. Common Opal with a lemon-yellow colour.
Levin Opal. Precious Opal with long and thin, lightning-like flashes.
Light Opal. Synonym of White Opal.
Lightning Ridge Opal. Opal from Lightning Ridge, New South Wales Australia. Although different forms of Opal are found there, this term usually represents the high quality Black Opal found there.
Lithoxyl Opal. Wood Opal where the original structure of the tree is very apparent.
Liver Opal. Synonym of Menilite (below)
Myrickite black glass. A yellow-green Common Opal with black inclusions an imitation Opal produced from resin
Menilite. Opaque, greyish-brown form of Common Opal. Also known as Liver Opal.
Mexican Fire Opal. Form of transparent Opal from Mexico, usually with an orange or red colour, highly desired as a gem. Although scientifically considered a Common Opal, it is rather rare and much sought after. If it exhibits a play of colour, it is known as Precious Fire Opal.
Milk Opal. Opal with a milky-white colour. Controversy exists whether the name Milky Opal is coined for a milky white Common Opal or a milky white Precious Opal.
Moss Opal. Common Opal containing inclusions resembling moss.
Mother of Opal. Precious Opal with bright colour specks filling the pores of sandstone or ironstone.
Mother of Pearl Opal. Banded Opal used as cameos.
Mountain Opal. Opal from igneous environments. Also called Volcanic Opal.
Neslite. Common Opal similar to Menilite, but darker grey in colour. It was once a popular material for sword handles.
Nevada Opal. Opal from the Virgin Valley (Humboldt Co.), Nevada.
Onyx Opal. Common Opal resembling banded Onyx.
Opal Matrix. Thin layer of Precious Opal on host rock. Small rock fragments are used in jewellery.
Opaline. Opaline is synonymous with Opal Matrix (above), but was also an old term used to describe Opal from Australia.
Opalite. Opalite has many connotations. It may refer to an impure form of Opal
Opalized Bone. Synonym of Bone Opal
Opalized Fossil. Synonym of Fossil Opal
Opalized Shell. Synonym of Shell Opal
Opalized Wood. Synonym of Wood Opal
Painted Boulder. Sandstone boulders with a coating of Precious Opal. When used in jewellery, this term is synonymous with Opal Matrix.
Pearl Opal. Synonym of Tabasheer
Pineapple Opal. Opal pseudomorph after Ikaite that resembles a pineapple. It is found only in White Cliffs (New South Wales), Australia. The pseudomorphed mineral was originally thought to be Glauberite, but studies now prove it to be Ikaite.
Pinfire Opal. Precious Opal with very small, pinhead-size colour flashes.
Pinpoint Opal. Australian synonym of Pinfire Opal
Pipe Opal. Opal formed as a filling of long, cylindrical cavities in rock. Pipe Opals range in size from several inches to many feet.
Pitch Opal. Yellow to brown Common Opal with a pitchy lustre.
Potch. Australian term for Common Opal.
Prase Opal. Green to dark green form of Common Opal.
Precious Fire Opal. Fire Opal displaying play of colour.
Precious Opal. Any Opal exhibiting a play of colour.
Prime d'Opal. Synonym of Mother of Opal
Pyrophane. Precious Opal in which the play of colour wanders about and reappears at random. This term is sometimes incorrectly used to describe Girasol.
Queensland Opal. Synonym of Boulder Opal
Quinzite Opal. Rose to pink coloured Opal. It is usually without play of colour, but a few examples displaying play of colour are known. Quinzite Opal is synonymous with Quinzite, Quincite, Quincite Opal, and Rose Opal.
Radiolite Opal. Common Opal of a smoky-brown colour caused by inclusions of the exoskeletons of a unicellular marine organism known as radiolaria. May also be called Radio Opal.
Rainbow Opal. Precious Opal where the play of colour is seen in curved bands, somewhat resembling a rainbow.
Red Flash Opal. Precious Opal with red colour flashes that swiftly appear and disappear as the stone is rotated.
Resin Opal. Common Opal with a yellow-brown colour and resinous lustre.
Rumanite. Opal from Romania.
Seam Opal. Opal found in the seams or large cracks of rock. May also specifically refer to masses of white Common Opal containing bands of precious White Opal.
Semiopal. Term sometimes used to describe any type of Common Opal, but many times alludes to particular forms of Common Opal, such as Wax Opal, Prase Opal, etc. Semiopal is also written as Semi-opal, and is synonymous with Half-opal.
Shell Opal. Opal pseudomorph after a shell.
Slocum Stone. A synthetically grown Opal. Also called Slocum Opal.
Sun Opal. Name that describes several types of Opal. May refer to Fire Opal, Mexican Fire Opal, Honey Opal, or Amber Opal.
Tabasheer. Opal occurring as an organic by product. It forms by the hardening of a secretion issued from certain bamboo, forming a porous, rounded mass of Opal.
Virgin Valley Opal. Opal from the Virgin Valley (Humboldt Co.), Nevada.
Wash Opal. Waterworn Opal pebbles from alluvial deposits.
Water Opal. Synonym of Jelly Opal
Wax Opal. Yellow to brown Common Opal with a waxy lustre.
White Cliffs Opal. Opal from the White Cliffs, New South Wales, Australia
White Opal. Precious Opal with light body colours (white, yellow, cream, etc.). Differentiated from Black Opal, which has a dark background colour.
Wood Opal. Any Opal that formed a pseudomorph after wood from a tree, and retains the original shape and appearance of the wood. Wood Opal may refer to both Common Opal and Precious Opal, but the term usually refers to large pieces of Common Opal.
Yowah Nut. Small, rounded form of Boulder Opal from Yowah (Queensland), Australia in a nodules embedded in ironstone. Closely related to Boulder Opal, it occurs most often as walnut-sized ironstone nodules containing pockets, veining, or sprinklings of vivid Precious Opal.
