Australian Light Opal 16.17 Carats Loose (Unset) Gemstone ready for setting in jewellery or as an addition to an Opal collection. Australian Opal is classified by the Opal industry as Natural Opal Type 1, 2 or 3 Opal is defined when the Opal is presented in one piece in its natural state apart from cutting or polishing, and is of substantially homogenous chemical composition. Genuine Natural Australian Opal is Australia s National Gemstone and the State Emblem of N.S.W., the lucky gem from the lucky country. A hydrated amorphous form of silica SiO2nH2O consisting of spheres of silicon dioxide molecules arranged in regular, closely packed planes. And only found in N.S.W., South Australia and Queensland. All Australian Opal Cutters Opals are Guaranteed to be completely natural and are free of dyes and any artificial colours or colour enhancing treatments. With Base tones ranging from Black (N1-N4), Dark (N5-N6) and Light (N7-N9). Opal is arguably the worlds most valuable commercially available gemstone with Gem Opals (with bright colours and patterns) are estimated to be 5,000 times rarer than diamond. Light Opal is classified by the Opal industry as Natural Opal Type 1. Genuine Natural Australian White Opal occurs in limited quantity in all of the Australian Opal fields but is predominantly from Coober Pedy in South Australia. Traditionally known as white opal, the Opal displays pure hydrated silica SiO2 nH2O with elements of Magnezium Oxide present giving the opal a white base tone. Precious light Opal shows a variable interplay of internal colors, and though it is a mineraloid, it has an internal structure. At microscopic scales, precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic close-packed lattice.