Lightning Ridge is a small outback town in north-western New South Wales, Australia. Part of Walgett Shire, Lightning Ridge is situated near the southern border of Queensland, about six kilometres east of the Castlereagh Highway. The Lightning Ridge area is a world-renowned centre of the mining of black opals and other opal gemstones. It was later renamed by the New South Wales Lands Department as Warrangulla but after World War I it was named Lightning Ridge. It is claimed that the name dates back to the 1870s when a farmer, his dog and 600 sheep were all killed by lightning. It is almost certainly an outback myth. The town, being in the inland regions of Australia does have some spectacular lightning storms come through the region often. The town has a famous opal and gem show that is held annually. Lightning Ridge is an important paleontological site, with fossils dating back to the Cretaceous period, 110 million years ago. The sandstone rock once formed the bottom of a shallow inland sea where the remains of aquatic plants and animals were preserved. The site is especially important as a source of fossils of ancient mammals which, at that time, were small creatures living in a world dominated by dinosaurs. The fossils are sometimes opalised and discovered by opal miners. Important discoveries at Lightning Ridge include the ancestral monotremes Kollikodon ritchiei and Steropodon galmani.
Black Opal is the most rarest type of Opal, only found in a very few places in the world (mainly Lightning Ridge in NSW, Australia however some has been found in Mintabie and other small mine sites). Black Opal is non transparent. If you shine light onto it you will not be able to see through the Opal. It is made up of potch and magnificent colours and patterns. Because Black Opal is so rare and also so beautiful, it is the most expensive type of Opal you will find. Black Opal is purchased for investment, as well as for jewellery making or simply just as souvenirs of Australia. Black opal is classified as opals that have a dark body tone of N1-N4.The term Black Opal does not mean that the Opal is dull or dark. Some of the brightest and most beautiful opals are Black Opals. The term simply refers to the body tone of the stone.
Dark Opal is also found in the same region as Black Opal; in Lightning Ridge. It has a dark body tone but not dark enough to be classified as a Black Opal. Dark Opals have a body tone of N5 to N7.
Lightning Ridge has also produced Crystal and White Opals from the mining efforts there. Some of these opals are very spectacular and are easily distinguishable as Lightning Ridge grade in comparison to the White and Crystal Opal that has been discovered in Coober Pedy. Some Crystal Opal has dark body tones which has been given the name dark crystal opal or black crystal opal. These are semi transparent crystals that are very dark or black inside.