BLACK OPAL. 1970's jewellery. A Creative Black Opal and Diamond Ring. A stunning yet unusual ring composed of a central, oval black opal cabochon mounted in a bold textured, abstract mount highlighted with a row of 5 brilliant cut diamonds. All set in yellow. The opal measures 18x10mm weighing approximately 7-8cts and the diamonds weigh approximately 0.25cts in total. Shank stamped 18ct and PM. 25 grams.
February 15th 1971- Decimalisation Day: - The United Kingdom and Ireland both switch to decimal currency.
SOURCES OF OPAL. Until the nineteenth century the only source of precious opal known to Europeans was the mining district of Červenica, then in Hungary, now Slovakia. Opal without play of color is very common and can be found all over the world, unlike precious opal deposits that are in greater scope found today only in Australia, U.S. and Mexico. Australia produces around 97% of the world's opal. 90% is called 'light opal' or white and crystal opal. White makes up 60% but not all the opal fields produce white opal; Crystal opal or pure hydrated silica makes up 30%; 8% is black and only 2% is boulder opal. The town of Coober Pedy in South Australia is a major source of opal. Another Australian town, Lightning Ridge in New South Wales, is the main source of black opal, opal containing a predominantly dark background (dark-gray to blue-black displaying the play of color). Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix. It is found sporadically in western Queensland, from Kynuna in the north, to Yowah and Koroit in the south.
A Vintage black Opal ring. A 1970's jewel. A Black Opal and Diamond Ring. Opal 7-8cts approx. Designed by Peter Minturn.