Opal is found all over the world (Brazil, Mexico, Honduras, and the western United States), yet Australia produces 95% of the world's precious opal and is our official national gemstone. See Google Arts and Culture: Australian Opals). Wondering if you can find opal in Louisiana from every state? The answer is yes, and it's called Louisiana Sand Opal. These rare types of opal are a type of sandstone that was once mined in the Catahoula Formation in Leesville.
Opal is found all over the world, but not everything is valuable or sought after by collectors. Because it is located between three states that produce American opals (Arizona, Nevada, and Idaho), it stands to reason that Utah also has opals. In an attempt to match the brilliance of precious Australian opals, Ethiopian opals are often chemically treated to increase their color intensity. South Australia is the largest producer of opal in terms of volume and produces white opal or the “milky” type of opal.
White Cliffs also stands out for producing “opal cones”, a strangely shaped fossil of opal in the form of mineral crystal. The formation of opal dates back millions of years, when Australia became a new continent covered by a vast inland sea with a sedimentary basin. Opals hide in rhyolite geode mineraloids that form in low-temperature silicon dioxide cracks in the earth. These are “composite” stones and feature a thin sheet of genuine opal on the surface and then backed by other materials or metals.
These wild lunar landscapes are known for their really bad weather conditions, but it seems that nothing can discourage people from their search for opals for more than a century and a half. Australia and Ethiopia are the most competitive markets for producing opals with different color games. A well sinker, named Larry O'Toole, is credited with finding the first opal at Mintabie in the 1920s. Ancient miners claim that opal was first discovered in Lambina during the depression years of the early 1930s.
The Coober Pedy opal mining fields are located in the interior of South Australia, Stuart Range, 750 km north of Adelaide. These rare fossils form when a mineral crystal of glauberite (or ikalite) is first replaced by calcite and then opalized. The amount of opals discovered here is not recorded, but opals often come to the surface while extracting desirable agates. Every year, more and more fortune seekers and enthusiastic tourists visit the opal mines trying their luck finding precious stones.