Guest Author - Michelle R. Mangio
Known as Australia's national gemstone, the Opal is an extraordinary and beautiful gemstone. Its beauty is created by the diffraction of white light into colors of the spectrum by the unique lattice of silica spheres in the gem. This is similar to the phenomena that causes rainbows or the effect of oil on water.
Since the 1880s, Opal has been mined in the outback of Australia. Today, more than 95% of the world's opal is produced in Australia. The three primary locations for Opal fields are Lightning Ridge in New South Wales, Coober Pedy in South Australia, and Queensland fields.
Lightning Ridge is home to the world famous black opal and has supplied the highest quality black and crystal opal since the early 1900s.
Coober Pedy is possibly the most famous opal mining town, both because it was once the largest opal producing region in the world and also that many homes, including the famous Desert Cave hotel, are located underground to avoid the high desert temperatures
Queensland fields produce boulder opal which forms in veins in the ironstone host rock.
Which leads, of course, to the question: what types of Opals are there?
Black Opal is the most valuable type of Opal, coming mainly from Lightning Ridge. High quality stones are rare, and thus very expensive. They are distinguised by the blackness of the background and the sharpness of the color within the stones.
Light Opal (also called White or Milky Opal) ranges from being transparent to nearly opaque and have a light or white body tone of background hue.
Crystal Opal includes light or black opal which is transparent or very translucent. Color can be seen from deep within the opal. After Black Opal, this is the most desired kind of opal.
Boulder Opal occurs naturally in hard rock, easily identified because when cut, the host rock (usually a brown ironstone) is left on the back of the opal. These are predominantly mined in Queensland.
You may also have heard of Doublet Opal and Triplet Opal. Double Opal is actually a slice of natural opal cemented to a darkened base material to enhance the natural color of the opal. Triplet Opal is a thin slice of natural opal with a dark base material and a transparent top layer, usually glass or quartz.
The value of an Opal is predominantly determined by the degree of brilliance. Patterns of color, especially when combined with brightness, may increase the value many times. Red orange colors are the might highly prized, but brightness still trumps color: a blue/green brilliant stone will still be more valuable than a dull red stone. It is best to consult an expert in determining the value of an opal.
Opals are truly symbolic of Australia, and there are many shops and opportunities to purchase Opals while visiting the country. The National Opal Collection not only sells Opals, but also has a museum exhibit, with more opalized fossils than any other establishment in Australia.
One of my personal favorite places to shop for Opals (and where I purchased my own) is Altmann & Cherney, a family-owned business with store locations in both Sydney and Melbourne. They are also home to the two most valuable Opals, the Olympic Australis (kept in Melbourne) and the Aurora Australis (the world's most valuable Black Opal, kept in Sydney). Both can be viewed during store hours. If you find yourself in Melbourne or Sydney, I highly recommend a stop at their store locations.
