Australian Triplet Opal 7x5mm 4x claw Earrings Set in Stainless Steel. Categorised as Natural Australian Opal Type 3 Triplet Opal is Genuine Natural Australian Gem Crystal Opal, a hydrated amorphous form of silica SiO2AnH2O consisting of spheres of silicon dioxide molecules arranged in regular, closely packed planes. Backed by Australian Black Opal and capped with a cabochon layer of silica quartz. The three layers have the same coefficient of thermal expansion and are guaranteed for life against delamination. Guaranteed free of dyes and artificial colour.