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Each of the three notable types of opal – precious, common, and fire [3] – display different optical effects; therefore, the intended meaning varies depending on context. The general definition of opalescence is a milky iridescence displayed by an opal, which describes the visual effect of precious opal very well, and opalescence is ...
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.
Chalcedony Ice-blue (boulder, polished section and cabochon in ring. In Greenland, white to greyish chalcedony is known from volcanic strata of the Paleocene, in the Disko-Nuussuaq area (West Greenland) and from the Scoresby Sound area (East Greenland).
Wood opal, also known as xylopal, [52] [53] is a form of opal, [54] as well as a type of petrified wood which has developed an opalescent sheen or, more rarely, where the wood has been completely replaced by opal. Other names for this opalized sheen-like wood are opalized wood and opalized petrified wood. It is often used as a gemstone. [55]
Examples of iridescence include soap bubbles, feathers, butterfly wings and seashell nacre, and minerals such as opal. Pearlescence is a related effect where some or most of the reflected light is white. The term pearlescent is used to describe certain paint finishes, usually in the automotive industry, which actually produce iridescent effects.
Hyalite is a transparent form of opal with a glassy lustre. It may exhibit an internal play of colors if natural inclusions are present. It is also called Muller's glass, water opal, and jalite. Müller's glass is named after its discoverer, Franz-Joseph Müller von Reichenstein.
Opalite is a trade name for synthetic opalescent glass and various opal and moonstone simulants. Other names for this glass product include argenon, sea opal, opal moonstone, and other similar names. [1] [2] It is also used to promote impure varieties of variously colored common opal. [1]
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]