A black crystal genuine gold hills opal ring is somewhat unique in that the gold or the jewelery musty come from the back hills of Dakota in the US, yet the opal is likely to be an Australia opal from the north of Australia.
The types of opals available include:
The Black Opal has a dark body tone than the white opal of course, which causes a brightness of color unmatched by the other opal types. Black Opals are only mined at Lightning Ridge in New South Wales in Australia and considered very rare and are consequently very expensive. White Opals, by contrast are almost cream and sometimes called a Milky Opal. Being white they do not show the internal color as much as the black and are generally bought as white opals only. In an excellent quality stone however there can still be seen some color flashing.
Boulder Opals are different again and have a solid layer of brown ironstone on the back of the stone. They originate from large ironstone bounders underground hence the name.
A Crystal opal can be the same as above but has a transparent or semi-transparent body tone which means you can see through the stone. Crystal opal can have a dark or light body tone hence, “black crystal opal” and “white crystal opal”.
A Fire Opal is an American term and describes any opal which has a significant amount of red coloring. Red is the rarest colour in opals, so these are quite valuable. Often confused with a ‘Mexican fire opal’ which is different yet again and displays orange instead of red coloring.
A Matrix opal is where the opal occurs as a network of veins or infilling of voids or between grains of the host rock. A Matrix comprises precious opaline silica as an infilling of pore spaces in silty claystone or ironstone. the matrix opal shows a fine pinfire colour in the natural state. very rare
Any of these opals, in fact, can be put into a gold hills opal ring but the black crystal tends to be the most popular of all.