OPAL OPAL Australian Boulder Opal is found in the desert of Queensland. This region is very harsh, with temperatures that reach over 120 degrees.
Opal mining is a very difficult process, and few mines prove to be successful.
Boulder Opal was formed milliions of years ago from a solution that flowed into seams, cracks, and cavaties in a type of sandstone known as Ironstone. Opal is composed of an arrangement of very small silica spheres. The play of color that Opal is known for is the result of the diffraction of light by these spheres and the spaces in between them. Different colors are the result of different sized spheres. For example, the color violet comes from an arrangement of spheres which have diameters of 1,500 angstroms, and red comes from spheres that have diameters of 3,500 angstroms.