Opal Information : Where is opal found? How is opal mined? Different types of opal.
Following is an intentionally simple explanation of opals. This is to
give you a fast and easy way to understand opals.
Where is opal found?
Opal is found in Australia, Europe, Africa, USA, Mexico and South America.
However, the best opal is found in Australia and it is generally recognized that the best of that comes from the area
around the township of Lightning Ridge in the state of NSW. This is known as the black opal. Having said that you
shouldn’t think that opals from other regions of the world or Australia would be inferior or less beautiful.
How is opal mined?
Black opal is mostly mined in underground operations, although in some cases it will be open
cut mining. A mine is dug by drilling a hole called a shaft about three feet in diameter. The
mine can be anywhere form ten feet to 70 feet or more in depth. From this hole drives are dug
radiating out to the perimeters of the claim. A claim is usually fifty feet long by fifty feet wide.
Often several layers.
Miners use various methods from machinery to hand tools to dig out the opal. It can
be found in seams of opal or in small nuggets called nobbies.
Fossiking is also popular with part-time miners who can search through mullock heaps (spoils from the mine)
to find their fortune.
Australian Opal types:
Black Opal from opal fields of New South Wales.
Black Opal ,White Opal, Grey Opal, etc are terms which relate to the base colour of the stone. Imagine pouring
some black ink into a glass of water, just enough so that you could still just see through it. Now throw in some
bright pieces of coloured plastic. You can see the bright coloured plastic pieces and they are in a black solution.
So the base colour is black! That’s what a black opal is like, the base colour is black and the other colours provide
the opal colour that we want to see. Without this black base you would be able to see right through the opal and it
would not display its colour as well. Now imagine a glass of milk and put some coloured pieces in it. That is similar
to White opal. Then we have crystal opal which is similar to the glass of water with no base colouring in it.
Then we have Boulder Opal which is mainly found near the Queensland. Boulder opal is mostly a thin layer of opal
sitting on top of a pieces of ironstone. We also have Yowah matrix which again is a hard stone with impregnations of
opal through it.
Solid, Doublet and Triplet.
Solid opals are one piece. They are cut from the rough opal into shapes and then polished ready for sale.
Doublets are two pieces. Sometimes a piece of opal is too thin and needs
a reinforcing back so the cutter glues a piece of non saleable dark opal to the back of the thin piece of good
colourful opal. He then cuts and polishes it. Doublets are structurally inferior to solids but a good doublet
will often cost more than a poor solid.
Triplets are three pieces. A triplet is a doublet which has a dome on top of
clear material which can be quartz or even glass. Triplets are inferior to doublets in general and are less expensive.
They can still make great pieces of jewellery and be very affordable.