This is a town famous for its rich, rare and glorious black opal. Black opal derives its name from the colour of the 'nobbies' or pieces of rough opal in which the gems are usually found. Lightning Ridge is located 770 kilometres northwest of Sydney in an area that also produces wheat, sheep, cattle and oilseeds. Black opal was first discovered at Lighting Ridge in the late 1880s however, its commercial value was not at first recognised by buyers. Mining actually commenced in the early 1900s when some opal nobbies were found and trial shafts erected. Opal occurs at Lightning Ridge either as 'nobbies', or in seams and thin layers within vertical or horizontal joint plains, in a soft greyish claystone that hardens and whitens on drying. This claystone is commonly referred to as 'opal dirt'. The opal dirt levels occur between 6 and 18 metres from the surface, but have been known to go as deep as 30 metres. The fields also yield opalised shells, wood, and reptilian bones of the Cretaceous age. Some of the traditional fields around Lightning Ridge include the Three Mile and Thorleys Six Mile however, most opal is now being found in newer areas away from the township.
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