On the 28th July 1994 Opal was declared to be the national gemstone of Australia. Australia supplies the world with 90 percent of Opal. In 1840 Opal had been discovered. In Australia German geologist, Professor Johannes Menge discovered a common greenish opal near Angaston (South Australia) near the north of Adelaide. Then in 1868 boulder opal was mined from this deposit and then it was sent to England for evaluation during 1873. Soon enough the boulder opal was then known as Barcoo opal.
1. How does it form?
Opal is similar to quartz, amethyst, and glass. They form by silica and water. Opals are created when weathered silica seeps into a little crack as gel. The silica contains a lot of water in it. It then mixes with sodium silicate also known as Water glass. As the water evaporates the gel hardens. If the water evaporates to quickly then the opal will crack but if it evaporates slowly will be stable and also if it has a nice fire it will be considered a gemstone.
2. How is it mined?
Here are 4 ways of how they mine opal. First the simplest way is shaft sinking with a pick and a shovel. A shaft is sunk straight down until it hits the opal dirt. And then a handpick or screwdriver is used to extract the opal found. The second one is open cut mining. This is done by
a heavy machinery to remove large amounts of the opal dirt. This way of mining is much more expensive. The third one is noodling. Many locals search though mull rock for pieces of opal. They use a rake and sieve for tools. Some have a machine noodling by allowing big amounts of opal dirt to travel on a conveyer belt under ultra violet light, which can detect opal. The last one is Puddling and Rumbling. A puddler is a large mesh lined drum attached to a motor. It rotates and turns the clay into sludge water and then it is pumped into the drum. Then it escapes through the mesh.
3. Who is the mining company?
This mining company is GM which means great mining.
4. Where do the materials go-are they exported to other countries to factories?
Australia produces around 95% of the worlds opal is used in jewelry. Other countries which only have a little bit of opal are Honduras, Mexico, former Czechoslovakia, and Brazil. Butall these opals look different when they are found. Australian opal is the finest in the world. They export it to many countries.
5. What are they used for?
Opal is not really used for that many things. Mostly opal is used for jewelry. It is used for jewelry because it is very beautiful and it has a very soft stone. It can be sometimes used for buttons, furniture inlay, and small sculptures.
6. Is it valuable?
It is important to know what type of opal you have because the colour usually depends on how valuable it is. The black opal is more valuable than the boulder opal it is also more valuable than the light opal. The darker the body colour, the more valuable the gem. Red fire opal is the most rare. Followed by green, orange, green/blue, and blue. But also the pattern and clarity of an opal also counts. So if a blue/green had a cool beautiful pattern it could cost more than the red.
7. Does your country depend on these minerals being mined?
The Australian export market for opals is at estimated at $60 million with 165 billion in total mineral exports, therefore Australia does not rely on these minerals as a source of money.
Bibliography
"Valuing Opals." Costello's - Your Online Jewellers. Web. 14 Apr. 2011.
"Opal - Australia's National Gemstone." Welcome to the Website of the Gemmological Association of Australia. Web. 14 Apr. 2011.
http://www.greatmining.com/
"What Is Opal Specifically Used for Other than Jewelry? - Yahoo! Answers." Yahoo! Answers - Home. Web. 14 Apr. 2011.
"Australia's Energy and Mineral Export Earnings Record High in 2010 - Commodities & Futures." IBTIMES.com: International Business News, Financial News, Market News, Politics, Forex, Commodities - International Business Times. Web. 14 Apr. 2011.
Excellent! I never knew how opals were mined before. That was the most interesting for me. I also like that you recognized the resources you pulled information from.
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