Opal is composed of minute particles of silica in a closely packed spherical arrangement. Millions of years ago volcanic action caused the silica to flow into the cracks and crevices in the sedimentary strata of the earth’s crust. From time to time his molten rich silica replaced the host item it engulfed. Over the ages of volcanic eruptions and the drying of Australia’s inland sea to a desert, sea and plant life became trapped over time in the layers of the earth’s crust and the molten silica replaced them with the embryo of Australian opal. This is why opalized sea shells, ‘pipe’ opal (a tentacle of a squid) and even opalized dinosaur bones can be found some 600 miles from the nearest ocean.

Black opal is characterized by a dark body tone. This dark tone causes all light to diffract so that every bit of color the opal holds within, will be seen by the viewer. 

Found mainly in South Australia at Coober Pedy and Andamooka. Gem quality light or white opals show brilliant reds, greens and blues intermingled in a white or light background.

Found in both Lightning Ridge and South Australia. Jelly opal and crystal opal are solid opal, just a different type. Jelly opal, semi-crystal opal and crystal opal are all transparent or translucent. When they come from Lightning Ridge they have a darker tinge than the jelly and crystal opals from South Australia. In Lightning Ridge you mine nobby opal and seam opal. Nobby opal is the most prized and most expensive of all opals.

A jelly opal or crystal opal is basically speaking a solid nobby black opal that doesn't have the natural black or gray backing on it which stops the light from passing through the opal and also makes it opaque unless viewed from an angle. What distinguishes a jelly opal from a crystal opal is the brightness, sharpness and intensity of color, crystal opal is much more highly prized than jelly opal.

Found in South Western and Central Queensland, this beautiful variety of opal can be very similar in appearance to Black Opal and forms naturally within ironstone "Boulder" which is cut to form part of the gemstone. The opal is naturally attached to the host rock in which it was formed and when cut this host ironstone rock is left on the back to enable all colors to be refracted to the viewer.

A s in the case of South Australian and Lightning Ridge opal the silica may have replaced other organic material making it possible to find the most amazing opal fossils. Like the famous and magnificent “Yowah Nut” from central Queensland is one such occurrence, with its many veins of magnificent opal weaving it’s way through the ironstone host in ‘rivers’ and specks of glorious color. Many times when boulder opal is cut, some of the natural occurring ironstone is left in the face (top) of the opal, distinguishing it from the Lightning Ridge black opal.