Opal is an iridescent stone that can range in color from transparent clear to black, white, blue, red, and most other colors of the spectrum. Opal deposits are most common in Australia, but can also be found in the U.S. and Mexico, Hungary, and the Czech Republic. It is not crystalline in nature, so it is technically classified as a mineraloid with the structure SiO2 · nH2O.
5.50 - 6.50
1.980 - 2.250