Opals are the birthstone for October and are also associated with the Star Sign of Libra. They are believed to aid inner beauty, faithfulness and eyesight. The Australian Aborigines believe opal to have spiritual value. Opals come in a variety of colors, probably the most well known being white with sparkles of color, known as play-of-color and black opals which actually  have a dark blue or green base. Durability and Care  The hardness of an Opal ranges from 5.5 - 6 on The Mohs Scale, making them a fairly soft stone in comparison to say Sapphires and Rubies. You should protect your opals from chemicals, prolonged direct sunlight, any type of oil or grease and high heat.  Since opals contain 5 - 10 percent water it is possible they could dry out or craze. Clean your opal jewelry with care, wash in mild soapy water with a soft cloth. Did you know...  Opals have been on earth for thousands of years but only more recently discovered in Australia. Black opals from the Lightnening Ridge field, New South Wales, Australia were not discovered until around 1905, these are considered the most valuable, and a quality stone can be extremely expensive on a par with, or more than diamonds.  Whilst white opals were discovered in Queensland and New South Wales around 1887.  Australia has since been considered the world's primary source for precious opals. For about 1000 years, Hungary was the main supplier of opal and they also supplied many of the European monarchy/rulers and clergy. For a while, opals fell out favor and were seen as a symbol of bad luck. This, following the publication of a novel in 1829 by Sir Walter Scott in which the storyline led the public to believe that an opal had caused misfortune to befall the heroine.  However, the fact that Queen Victoria fell in love with opals, and together with her passion for the stone was enough to help restore the stones popularity. References Gemstones/Cally Hall, Dorling Kindersley Limited 1994 International Colored Gemstone Association http://www.gemstone.org Guide to Gems and Precious Stones (Simon & Schuster 1986) Gemstones of the World by Walter Schumann (sterling Publishing Co., Inc.) Tweet

Specific Gravity 2.10

Refractive Values 1.37 - 1.47

birefringence (doubly refractive gems only) None

Lustre Vitreous