Solid Australian Black Opal for Jewelry
FACTS ABOUT OPALS
When dinosaurs roamed the earth, the process of creation forged a unique gem which somehow appeared to entrap fire and light in a myriad of colours and thus OPAL was born. Opal is the most colorful of all gems. Its splendid play of color is unsurpassed, and fine examples can be more valuable than diamond. The play of color consists of iridescent color flashes that change with the angle at which the stone is viewed. This phenomenon is often called opalescence. The play of color may consist of large, individual flashes of color or may be of tiny, dense flashes. The intensity and distribution of the color flashes is a determining factor in the value of an opal.
Opals displaying play of color are known as precious opals, and opal lacking play of color are known as common opal. Gems are cut from the precious form. The most desired and beautiful form of opal is black opal, which is opal with a dark background with a strong play of color.
Technical Details
Chemical Composition and Name - SiO2nH2O (Hydrous Silicon Dioxide)
Hardness - 5.5 to 6.5
Refractive Index - 1.44 to 1.47
Specific Gravity - 1.95 to 2.20
Crystalline System - Gel
Other Optical Properties - Isotropic
