O – Opals
WHAT IS OPAL?
Opal is one of the world's most beautiful and precious gemstones, predominantly found in Australia. It is one of only six types of precious gemstones found on planet earth, sharing prestigious company with diamonds, rubies, sapphires, emeralds, and pearls. Over 95% of the world's precious opal comes from Australia, and opal is Australia's national gemstone.
Currently, Australia produces around 95% of the world's opal for use in the jewellery industry. Other countries in which opal is found in small amounts include Honduras, Mexico, former Czechoslovakia, and Brazil, however these types of opal often differ in appearance. Australian opal is considered the finest in the world.
The Australian export market for opals between 2000 and 2005, production figures for uncut gems varied between $100 million and $200 million.
Australia's Opal fields lie in the three states of Queensland, New South Wales, and South Australia, along the site of the ancient 'Great Inland Sea', or 'Great Artesian Basin'. White, or 'Milky' opal, is found in South Australia, Black opal is found in Lightning Ridge, NSW, and Boulder opal is found in Queensland.
The best time to visit the opal fields is April to September. Summer should be avoided due to the high temperatures and possible heavy rains making road access impossible in some areas.
Black Opal 
Black opal is characterised by a dark body tone causing brightness of colour which is unmatched by lighter opals. Black Opals are usually mined in Lightning Ridge, New South Wales, and are the most famous, and sought-after type of opal. The term 'black opal' does not mean that the stone is completely black (a common mistake), it simply means the stone has a dark body tone in comparison to a white opal.
White Opal 
White Opal - Also known as 'milky opal', white opal features light white body tones, and is mined in South Australia. White opal is more common and because of its body tone, generally does not show the colour as well as black opal. Nevertheless, white opals can still be absolutely magnificent in colour.
Boulder Opal
Boulder opal forms on ironstone boulders in Queensland. This type of opal is often cut with the ironstone left on the back, as the opal seam is usually quite thin. Leaving the ironstone on the back means that boulder opal can be very dark and beautiful in colour. The opal forms within the cavities of the boulders in both vertical and horizontal cracks. Boulders vary in shape and size, from as small as a pea, to as big as a family car. Boulder Opal has a tendency to cleave; when cleaved the "split" leaves two faces of opal, with a naturally polished face.
Crystal Opal 
Crystal opal is any of the above kind of opal which has a transparent or semi-transparent body tone - i.e. you can see through the stone. Crystal opal can have a dark or light body tone, leading to the terms "black crystal opal" and "white crystal opal.
AUSTRALIAN OPAL MINING FIELDS
Where are the opal fields in Australia?....Although there are lots of opal mining towns in Australia there are four which have become household names –Coober Pedy and Andamooka in South Australia and White Cliffs and Lightning Ridge in New South Wales. They are wild and unruly places surrounded by a moonscape of mullock humps where people fight against horrendous climate conditions in their search for precious gemstones. They are, as one observer noted, 'monuments to the tenacious optimism of all mankind'.
Opal Mines are indicated by an Orange dot
Tags: Gemstones Minerals
