Notable Australian Opal
Major finds of Australian opal are best known from specific localities, including the following:
1, Lightning Ridge: black opal in nodules, world's finest of this material; first mined commercially about 1905.
2, Grawin Opal Field, about 25 miles SW of Lightning Ridge, produces light-colored seam opals.
3, Coober Pedy, South Australia: modern mining began here about 1915; only white opals found here, in sandstone and claystone matrix, but some very fine.
4, Andamooka, South Australia: opals found here about 1930; very distinctive opal, white and also brownish in color; may be artificially blackened to enhance the appearance of the fire in the matrix.
5, White Cliffs area: started about 1889, but the opal is usually small, with veinlets of precious opal within common opal.
6, Gabanintha (Murchison Goldfield): bright green opal, colored by copper, found in quartz.
7, Mintabie: mined since 1931, about 350 km northwest of Coober Pedy. This area has now been extensively prospected.