Opals

=Opals=


 * [[image:P1070805-1.JPG caption="Specimens of Australian opals in our Museum"]] || [[image:den-opals.jpg width="218" height="320" caption="Opals close-up"]] ||
 * [[image:Opal-in-rough-pic.jpg width="281" height="227" caption="Opals in the rough"]] ||

Australian Opal Fields.
140 million years ago much of Central Australia was an inland sea and fine sands rich in silica were washed up on its shores. Silica is a mineral which is the main ingredient in beach sand. It is used for making glass. When the sea receded it formed the Great Australian Basin. 30-40 million years ago heavy weathering dissolved some of the silica and formed a gel. This gel then seeped into cracks in the ground and over many more million years eventually hardened into opal. Like opals, the "silica gel" in these little packets are made of silica.The packets are put with equipment that needs to be kept dry, for example cameras. Both "silica gel" and opals can hold a large amount of water. Gemstone opals usually contain less than 10% water. Unlike other gemstones, opals are not made up of crystals -they are made up of silica and water.
 * [[image:australia1.jpg width="323" height="263" caption="Great Australian Basin"]] ||
 * [[image:do-not-eat.gif width="120" height="163"]] || [[image:opals_main.jpg width="150" height="190"]] ||

Opal rainbow colours:
They are arranged together in a orderly 3D grid. Between the spheres is a silica and water gel. Light passes directly through the spheres but is bounced off the gel. Different sizes of spheres and different angles of bounce result in different colours. Smaller spheres display blue colours, larger spheres show orange and red. || The difference between common opal and precious opal is that the silica spheres in common opal are different sizes and not arranged in a uniform manner.
 * [[image:forms3.jpg width="222" height="106"]] || Opal is made up of tiny identical transparent spheres of silica.

Opal Drilling Gallery:

 * http://www.opalaustralia.com.au/bwWebsite/followon.asp?PageID=3042**
 * [[image:underground-digger.jpg width="221" height="154" caption="Underground hydraulic digger"]] || [[image:puddling-site.jpg width="223" height="149" caption="Puddling machines"]] || [[image:puddlers.jpg width="239" height="156" caption="Puddlers"]] ||

Visit an Opal Workshop and Gallery:

 * http://www.opalnet.com/menu2.html**
 * http://www.opalaustralia.com.au/bwWebsite/followon.asp?PageID=3043**
 * [[image:work02.jpg width="278" height="203"]] || [[image:opal-cluster.jpg width="220" height="206"]] ||