Lightning Ridge is known throughout the world for its magnificent black opal. The relatively young opal-bearing rocks occur in a belt about 70 km long by 30 km wide, with the town of Lightning Ridge in the approximate centre. A number of distinct opal fields are present through this belt, including the Lightning Ridge, Sheep Yard, Grawin, Carters Rush, Coocoran, Wyoming and Mehi fields.
Although the area is prone to a lack of outcropping rocks, some localities present reasonable exposures of the main rock types which make up the opal fields. Most opal mine dumps are composed of the sandstones which overlie the opal-bearing rocks, and an instructive view of the rocks from the surface to the opal-bearing strata can be viewed at the Three Mile open cut. The ground surface is strewn with small pebbles of quartz and small amounts of petrified wood, agate and rare topaz. Several large pits in the area give access to large amounts of the pebbles for fossicking.
The geological sites described in the downloadable tour guide include descriptions of a number of localities where the essential rocks of the area can be examined. In addition, a visit to the foreshores of the dry Coocoran Lake is described in terms of the landforms and processes active here. Detailed maps of the various opal fields about Lightning Ridge are also included in the guide.
An appropriate introduction to the attractions of Lightning Ridge can be gained from the Lightning Ridge Tourist Association web page.