Classified by the Opal industry as Natural Opal Type 1 Genuine Australian Black Opals are the most valuable and popular of all Opals and account for around 5% of Opals and is found at Lightning Ridge in Northern New South Wales. Black 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. Opal is Australias National Gemstone and the State Emblem of N.S.W., known as the lucky gem from the lucky country. A hydrated amorphous form of silica SiO2�?������?������???nH2O consisting of spheres of silicon dioxide molecules arranged in regular, closely packed planes. Australian Opal Cutters Opals are Guaranteed free of dyes and artificial colour. With Base tones ranging from Black (N1-N4) Black Opals with evidence of Iron Oxide and mined from Lightning Ridge that have a base body tone of (N5-N6) are today defined as Dark OpalsA�?������?������??? (which in the past have sometimes been referred to as GreyA�?������?������???, DarkA�?������?������??? or Semi-BlackA�?������?������???) and have been mined in fields such as Mintibie and found in limited quantities in various Other Opal mining fields.