![]() Fire opals that do not show play of color are sometimes referred to as jelly opals. The Fire opal is a term not commonly used within Australia but most famous source of fire opals is the state of Querétaro in Mexico these opals are commonly called Mexican fire opals. Although it does not usually show any play of color, occasionally a stone will exhibit bright green flashes. Boulder Opal has a tendency to cleave when cleaved the "split" leaves two faces of opal, with a naturally polished face.įire opal is a transparent to translucent opal, with warm body colors of yellow to orange to red. Boulder opal can be black or light depending on the appearance of the stone when viewed from the surface. Boulder opal occurs as in-fillings of cracks or voids usually in ironstone boulders. ![]() It mainly occurs in specific locations over a wide area of Western Queensland. Often just a thin vein of precious opal is present. Nevertheless, white opals can still be absolutely magnificent in colour if a good quality stone is found.īoulder Opal Specimen by Dieter Rosenkranz Australiaīoulder is a variety of precious opal that has the host rock forming naturally as part of the gem. White opal is more common and because of its body tone, generally does not show the colour as well as black opal. Some people refer to these as "white" although this expression should only be used where the body colour is very milky. White opals with a base tone ranging from colourless to medium grey are called light opal. ![]() Easily distinguished by the blackness of the background "body tone" or body colour. The term 'black opal' does not mean that the stone is completely black (a common mistake), it simply means the stone has a dark body tone in comparison to a white opal. credit : Nur Rachman Effendiīlack Opal is the most valued of Opals and comes mainly from Lightning Ridge. There are other kinds - fire opal, hyalite, water opal, hydrophane and honey opal. There is black opal, white opal, crystal opal and jelly opal. There are many different types of natural opals. Opal is the national gemstone of Australia. When it is transparent or very translucent, and the colour clarity is sharp, it is often referred to as crystal opal. Transparency - Opal of any body colour will be opaque, translucent or transparent. The variety of natural opal is determined by the two characteristics of body tone and transparency.īody Tone - The base tones of light, dark and black opal range from colourless, white, through the various shades of grey, to black. Precious Opal - is opal which exhibits the phenomenon known as play of colour, which is produced by the diffraction of white light through a micro-structure of orderly arrayed spheres of silica.The internal structure of precious opal makes it diffract light depending on the conditions in which it formed, it can take on many colors. ![]() It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. nH 2O), Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals.Opal is a hydrated amorphous form of silica (SiO 2 Photo: Amazing Geologist page on facebook
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