DETAILS

Opal is the non-crystalline form of the mineral Silica formed from a solution of Silicon Dioxide and Water. It is amorphous, void of a crystalline structure, and not a true mineral due to its lack of crystal forms. This hydrous Silicon Dioxide stone is referred to as a mineraloid. Opal is one of the most precious gemstones. Its name actually derives from the Latin word “opalus” and the Sanskrit word “upala”, both meaning “precious stone”. Opals are popular; Black Opal, White Opal, and Precious Fire Opals hold the highest price tag. Opals come in all sorts of base colors. They are often multicolored or banded and several different varieties exist. Common Opal is found worldwide. Notable deposits of all varieties of Opal include USA (Oregon, Nevada, Idaho, California), Australia, Mexico, Ethiopia, Peru, Madagascar, Czech Republic, Brazil, Honduras, and Canada. A key characteristic of Opals is their fluorescence. They are formed and found in all mineral environments, especially igneous. The wide array of majestic coloring that Opal displays has been a conundrum until in the 1960s when they discovered using an electron microscope that Opal is composed of tiny Silica spheres neatly arranged in an orderly pattern that allows for light entering the stone to diffract into a wide spectrum of colors. An array of colors can be seen when turning or moving Opals. This phenomenon is called ‘Play of Colors’ and is a notable characteristic of Opals. The density and pattern of the aligned silica are responsible for the assortment of colors displayed within this mineraloid. This effect is not seen in Common Opals as its pattern of Silica spheres are often too compact or too disordered to allow light refraction. Opals are susceptible to a cracking phenomenon called crazing. It is not exactly known what causes this but specific locales tend to produce opals with a higher susceptibility. Uncut Opals are often stored in water owing to the fact that Opals have water in their base structure, ranging from 3 to 21% of their weight. If an Opal is removed from water to be cut, it should not be without its hydro source for longer than a couple minutes or its susceptibility to crazing greatly increases. A very gradual drying process diminishes the risk of crazing to occur, but care should always be taken when wearing, cleaning, or cutting opals.