Around the world, over 97% of opals are mined in Australia. The other fields like Ethiopia, Mexico and US also produce different qualities of opals. In jewellery industry, Australian opals and Ethiopian opals are mainly used. Sometimes, it is hard to differentiate whether it is an Aussie opal or Ethiopian opal. The easiest way to tell them apart is rinsing them in water. While Ethiopian opals will change colour when they are wet, Australian opals will keep their colour when get wet.
Precious Opal is a gemstone which has been used in Jewellery for a long time. Opal is seen as a soft gemstone comparing to sapphire, ruby and diamonds. But opal has a Mohs hardness scale of 5-6, which makes it durable in jewellery.
Precious Opal, as a gemstone, shows multi-color at different angles because of its silica structure. With different arrangements and sizes of the silica spheres inside the opal, it shows different colours, like red, orange, yellow, green, blue, etc. This is also what the precious opal famous for.
Normally, Natural Precious Opal can be categorised into following groups. Solid Black Opal, Solid Crystal Opal, Solid White Opal, Boulder Opal, Opal Doublet, and Opal Triplet.
Solid Opals are naturally grown under earth and cutted in different shapes when they are mined out without any treatment and manmade composition. The whole piece of the gemstone is opal. It is very easy to tell the differences among the solid black opal, solid crystal opal and solid white opal by their body tone. Solid black opal, as its name shows, has a black or dark body tone. ( * Due to the degree of the black body tone, a few more different groups of opals can also be categorised into.). Solid Crystal Opal has a more transparent body tone, just like the crystal, whereas solid white opal has a more opaque and milky body tone.
Boulder opal is a vein of precious opal naturally grows in an host stone. When opal cutters cut it out, it shows as a layer of precious opal on top of an ironstone.
Opal doublet has two layers, top layer is natural precious opal and the base is ironstone, plastic or other manmade materials. Doublets are produced afterward by gluing one layer of natural precious opal on a manmade base. The reason to product doublets is to get the beauty of natural precious opal at a relative low price. So buying a jewellery with an opal doublet is a pretty nice choice to obtain the real beauty of the precious opal at a very economical price.
Opal Triplet has three layers, the top domed transparent layer is either manmade glass or plastic, the middle is a very thin layer of precious opal, and the base is manmade materials.