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The Koroit opal field is known for the very distinctive type of boulder opal that is found in its mines. In Queensland boulder opal is found within a 300 km wide belt of sedimentary rocks in the Winton Formation. Here opal is found as a kernel in small concretions. [1] The Koroit Opal field was discovered in 1897 by Lawrence Rostron.
The world's largest and most valuable gem opal "Olympic Australis" was found in August 1956 at the "Eight Mile" opal field in Coober Pedy. It weighs 17,000 carats (3.4 kg; 7.5 lb) and is 11 inches (280 mm) long, with a height of 4 + 3 ⁄ 4 in (120 mm) and a width of 4 + 1 ⁄ 2 in (110 mm).
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Meet the "Virgin Rainbow" – perhaps the finest and certainly the most expensive opal on record. It literally glows in the dark. In fact, as it gets darker around the opal, the opal appears ...
Andamooka Opal, presented to Queen Elizabeth II, also known as the Queen's Opal; Flame Queen Opal; Galaxy Opal; Halley's Comet Opal, the world's largest uncut black opal; Olympic Australis Opal, reported to be the largest and most valuable gem opal ever found
Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants. Silica is an amorphous metalloid oxide formed by complex inorganic polymerization processes.
The Galaxy Opal is the world's largest polished opal, certified by the Guinness Book of World Records in 1992. [1] It was found at the Boi Morto Mine in Brazil in 1976. [ 2 ] The finished opal weighs approximately 3,749 carats , or 0.75 kg.
Ammolite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America.It is commonly unearthed by natural erosion or through the process of various mining practices, within the perimeter of an ancient sea bed called the Western Interior Seaway. [2]