Rare OPAL natural Australia Fire SOLID Matrix BOULDER Gem Cabochon Estate Piece

Description: This specimen weighs weighs 0.30 carats, which is 0.06 grams, and measures 6 mm by 4 mm by 2.5 mm. I offer a shipping discount for customers who combine their payments for multiple purchases into one payment! The discount is regular shipping price for the first item and just 50 cents for each additional item! Please be sure to request a combined invoice before you make your payment. Thank you. Hi there, I am selling this really nice Boulder Opal Mineral Specimen Cabochon from Australia . It is really beautiful. It is a collection piece of mine that I have had. Times are tough and I am trying to raise money, and I thought I would try selling off some things from my old collection. I hope it finds a good home out there, and I am sure they will. This piece is really nice. I purchased it along with some other hand made cabochons from an estate of a really well known lapidary artist. All the cabs there were fabulous and hand designed. This opal is from Australia, and has TONS OF FIRE! It is beyond gorgeous and you will love it to death when you get it! If you have any questions, do not hesitate to ask me. Have fun bidding, and know that I will ship this out the same day as the payment clears. Thanks so much for visiting my auction and have a great day:>) Opal. Wikipedia article (link stripped) Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals. 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. Opal is the national gemstone of Australia. There are two broad classes of opal: precious and common. Precious opal displays play-of-color (iridescence), common opal does not. Play-of-color is defined as "a pseudochromatic optical effect resulting in flashes of colored light from certain minerals, as they are turned in white light." The internal structure of precious opal causes it to diffract light, resulting in play-of-color. Depending on the conditions in which it formed, opal may be transparent, translucent or opaque and the background color may be white, black or nearly any color of the visual spectrum. Black opal is considered to be the rarest, whereas white, gray and green are the most common. Precious opal shows a variable interplay of internal colors, and though it is a mineraloid, it has an internal structure. At microscopic scales, precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic close-packed lattice. It was shown by J. V. Sanders in the mid-1960s that these ordered silica spheres produce the internal colors by causing the interference and diffraction of light passing through the microstructure of the opal. The regularity of the sizes and the packing of these spheres determines the quality of precious opal. Where the distance between the regularly packed planes of spheres is around half the wavelength of a component of visible light, the light of that wavelength may be subject to diffraction from the grating created by the stacked planes. The colors that are observed are determined by the spacing between the planes and the orientation of planes with respect to the incident light. The process can be described by Bragg's law of diffraction. Visible light cannot pass through large thicknesses of the opal. This is the basis of the optical band gap in a photonic crystal. The notion that opals are photonic crystals for visible light was expressed in 1995 by Vasily Astratov's group. In addition, microfractures may be filled with secondary silica and form thin lamellae inside the opal during solidification. The term opalescence is commonly used to describe this unique and beautiful phenomenon, which in gemology is termed play of color. In gemology, opalescence is applied to the hazy-milky-turbid sheen of common or potch opal which does not show a play of color. Opalescence is a form of adularescence. For gemstone use, most opal is cut and polished to form a cabochon. "Solid" opal refers to polished stones consisting wholly of precious opal. Opals too thin to produce a "solid" may be combined with other materials to form attractive gems. An opal doublet consists of a relatively thin layer of precious opal, backed by a layer of dark-colored material, most commonly ironstone, dark or black common opal (potch), onyx, or obsidian. The darker backing emphasizes the play of color, and results in a more attractive display than a lighter potch. An opal triplet is similar to a doublet, but has a third layer, a domed cap of clear quartz or plastic on the top. The cap takes a high polish and acts as a protective layer for the opal. The top layer also acts as a magnifier, to emphasize the play of color of the opal beneath, which is often of lower quality. Triplet opals therefore have a more artificial appearance, and are not classed as precious opal. Jewelry applications of precious opal can be somewhat limited by opal's sensitivity to heat due primarily to its relatively high water content and predisposition to scratching. Combined with modern techniques of polishing, doublet opal produces a similar effect to black or boulder opal at a fraction of the price. Doublet opal also has the added benefit of having genuine opal as the top visible and touchable layer, unlike triplet opals. Fire opal is a transparent to translucent opal, with warm body colors of yellow to orange to red. Although it does not usually show any play of color, occasionally a stone will exhibit bright green flashes. The most famous source of fire opals is the state of Querétaro in Mexico; these opals are commonly called Mexican fire opals. Fire opals that do not show play of color are sometimes referred to as jelly opals. Mexican opals are sometimes cut in their rhyolitic host material if it is hard enough to allow cutting and polishing. This type of Mexican opal is referred to as a Cantera opal. Also, a type of opal from Mexico, referred to as Mexican water opal, is a colorless opal which exhibits either a bluish or golden internal sheen. Girasol opal is a term sometimes mistakenly and improperly used to refer to fire opals, as well as a type of transparent to semitransparent type milky quartz from Madagascar which displays an asterism, or star effect, when cut properly. However, the true girasol opal is a type of hyalite opal that exhibits a bluish glow or sheen that follows the light source around. It is not a play of color as seen in precious opal, but rather an effect from microscopic inclusions. It is also sometimes referred to as water opal, too, when it is from Mexico. The two most notable locations of this type of opal are Oregon and Mexico.Peruvian opal (also called blue opal) is a semi-opaque to opaque blue-green stone found in Peru, which is often cut to include the matrix in the more opaque stones. It does not display play of color. Blue opal also comes from Oregon in the Owyhee region, as well as from Nevada around the Virgin Valley. Opal is also formed by diatoms. Diatoms are a form of algae which, when they die, often form layers at the bottoms of lakes, bays, or oceans. Their cell walls are made up of hydrated silicon dioxide which gives them structural coloration and therefore the appearance of tiny opals when viewed under a microscope. These cell walls or "tests" form the “grains” for the diatomaceous earth. This sedimentary rock is white, opaque, and chalky in texture. Diatomite has multiple industrial uses such as filtering or adsorbing since it has a fine particle size and very porous nature, and gardening to increase water adsorption. Opal was rare and very valuable in antiquity. In Europe it was a gem prized by royalty. Until the opening of vast deposits in Australia in the 19th century the only known source was Červenica beyond the Roman frontier in Slovakia. Australian opal has often been cited as accounting for 95–97% of the world's supply of precious opal, with the state of South Australia accounting for 80% of the world's supply. Recent data suggests that the world supply of precious opal may have changed. In 2012, Ethiopian opal production was estimated to be 14,000 kg (31,000 lb) by the United States Geological Survey. USGS data from the same period (2012), reveals that Australian opal production to be $41 million. Because of the units of measurement, it is not possible to directly compare Australian and Ethiopian opal production, but these data and others suggest that the traditional percentages given for Australian opal production may be overstated. Yet, the validity of data in the USGS report appears to conflict with that of Laurs et al.[citation needed] and Mesfin,[citation needed] who estimated the 2012 Ethiopian opal output (from Wegal Tena) to be only 750 kg (1,650 lb). Australia Edit The town of Coober Pedy in South Australia is a major source of opal. 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).[26] The Mintabie Opal Field located about 250 km (160 mi) north west of Coober Pedy has also produced large quantities of crystal opal and the rarer black opal. Over the years, it has been sold overseas incorrectly as Coober Pedy opal. The black opal is said to be some of the best examples found in Australia. Andamooka in South Australia is also a major producer of matrix opal, crystal opal, and black opal. Another Australian town, Lightning Ridge in New South Wales, is the main source of black opal, opal containing a predominantly dark background (dark gray to blue-black displaying the play of color). Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix. It is found sporadically in western Queensland, from Kynuna in the north, to Yowah and Koroit in the south. Its largest quantities are found around Jundah and Quilpie in South West Queensland. Australia also has opalized fossil remains, including dinosaur bones in New South Wales[28] and South Australia,[29] and marine creatures in South Australia.[30] Ethiopia Edit Although it has been reported that Northern African opal was used to make tools as early as 4000 BC, the first published report of gem opal from Ethiopia appeared in 1994, with the discovery of precious opal in the Menz Gishe District, North Shewa Province.[31] The opal, found mostly in the form of nodules, was of volcanic origin and was found predominantly within weathered layers of rhyolite.[32] This Shewa Province opal was mostly dark brown in color and had a tendency to crack. These qualities made it unpopular in the gem trade. In 2008, a new opal deposit was found approximately 180 km north of Shewa Province, near the town of Wegel Tena, in Ethiopia's Wollo Province. The Wollo Province opal was different from the previous Ethiopian opal finds in that it more closely resembled the sedimentary opals of Australia and Brazil, with a light background and often vivid play-of-color. Wollo Province opal, more commonly referred to as "Welo" or "Wello" opal, has become the dominant Ethiopian opal in the gem trade. Gem grade Ethiopian Welo precious opal pendant Virgin Valley, Nevada Edit Multicolored rough opal specimen from Virgin Valley, Nevada, US The Virgin Valley[35] opal fields of Humboldt County in northern Nevada produce a wide variety of precious black, crystal, white, fire, and lemon opal. The black fire opal is the official gemstone of Nevada. Most of the precious opal is partial wood replacement. The precious opal is hosted and found in situ within a subsurface horizon or zone of bentonite, which is considered a "lode" deposit. Opals which have weathered out of the in situ deposits are alluvial and considered placer deposits. Miocene-age opalised teeth, bones, fish, and a snake head have been found. Some of the opal has high water content and may desiccate and crack when dried. The largest producing mines of Virgin Valley have been the famous Rainbow Ridge,[36] Royal Peacock,[37] Bonanza,[38] Opal Queen,[39] and WRT Stonetree/Black Beauty[40] mines. The largest unpolished black opal in the Smithsonian Institution, known as the "Roebling opal",[41] came out of the tunneled portion of the Rainbow Ridge Mine in 1917, and weighs 2,585 carats (517.0 g; 18.24 oz). The largest polished black opal in the Smithsonian Institution comes from the Royal Peacock opal mine in the Virgin Valley, weighing 160 carats (32 g; 1.1 oz), known as the "Black Peacock".[42] Mexico Edit Learn more This section does not cite any sources. Opal occurs in significant quantity and variety in central Mexico, where mining and production center on the state of Querétaro. In this region the opal deposits are located mainly in the mountain ranges of three municipalities: Colón, Tequisquiapan and Ezequiel Montes. During the 1960s through to the mid-1970s the Querétaro mines were heavily mined. Today's opal miners report that it was much easier to find quality opals with a lot of fire and play of color back then, whereas today the gem quality opals are very hard to come by and command hundreds of US dollars or more. The oldest mine in Querétaro is Santa Maria del Iris. This mine was opened around 1870 and has been reopened at least 28 times since. At the moment there are about 100 mines in the regions around Querétaro, but most of them are now closed. The best quality of opals came from the mine Santa Maria del Iris, followed by La Hacienda la Esperanza, Fuentezuelas, La Carbonera and La Trinidad. Important deposits in the state of Jalisco were not discovered until the late 1950s. In 1957, Alfonso Ramirez (of Querétaro) accidentally discovered the first opal mine in Jalisco - La Unica, located on the outer area of the volcano of Tequila, near the Huitzicilapan farm in Magdalena. By 1960 there were around 500 known opal mines in this region alone. Other regions of the country that also produce opals (of a lesser quality) are Guerrero, which produces an opaque opal similar to the opals from Australia (some of these opals are carefully treated with heat to improve their colors so high-quality opals from this area may be suspect). There are also some small opal mines in Morelos, Durango, Chihuahua, Baja California, Guanajuato, Puebla, Michoacán, and Estado de México. Other locations Edit Another source of white base opal or creamy opal in the United States is Spencer, Idaho.[43] A high percentage of the opal found there occurs in thin layers. Other significant deposits of precious opal around the world can be found in the Czech Republic, Canada, Slovakia, Hungary, Turkey, Indonesia, Brazil (in Pedro II, Piauí[44]), Honduras (more precisely in Erandique), Guatemala and Nicaragua. In late 2008, NASA announced it had discovered opal deposits on Mars.[45] The word 'opal' is adapted from the Latin term opalus, but the origin of this word is a matter of debate. However, most modern references suggest it is adapted from the Sanskrit word úpala.[50] References to the gem are made by Pliny the Elder. It is suggested to have been adapted from Ops, the wife of Saturn and goddess of fertility. The portion of Saturnalia devoted to Ops was "Opalia", similar to opalus. Another common claim that the term is adapted from the Ancient Greek word, opallios. This word has two meanings, one is related to "seeing" and forms the basis of the English words like "opaque"; the other is "other" as in "alias" and "alter". It is claimed that opalus combined these uses, meaning "to see a change in color". However, historians have noted the first appearances of opallios do not occur until after the Romans had taken over the Greek states in 180 BC, and they had previously used the term paederos.[50] However, the argument for the Sanskrit origin is strong. The term first appears in Roman references around 250 BC, at a time when the opal was valued above all other gems. The opals were supplied by traders from the Bosporus, who claimed the gems were being supplied from India. Before this the stone was referred to by a variety of names, but these fell from use after 250 BC. Historical superstitions Edit In the Middle Ages, opal was considered a stone that could provide great luck because it was believed to possess all the virtues of each gemstone whose color was represented in the color spectrum of the opal.[51] It was also said to grant invisibility if wrapped in a fresh bay leaf and held in the hand.[51][52] Following the publication of Sir Walter Scott's Anne of Geierstein in 1829, opal acquired a less auspicious reputation. In Scott's novel, the Baroness of Arnheim wears an opal talisman with supernatural powers. When a drop of holy water falls on the talisman, the opal turns into a colorless stone and the Baroness dies soon thereafter. Due to the popularity of Scott's novel, people began to associate opals with bad luck and death.[51] Within a year of the publishing of Scott's novel in April 1829, the sale of opals in Europe dropped by 50%, and remained low for the next 20 years or so.[53] Even as recently as the beginning of the 20th century, it was believed that when a Russian saw an opal among other goods offered for sale, he or she should not buy anything more, as the opal was believed to embody the evil eye.[51] Opal is considered the birthstone for people born in October.[54] The Olympic Australis, the world's largest and most valuable gem opal, found in Coober Pedy[55][56] The Andamooka Opal, presented to Queen Elizabeth II, also known as the Queen's Opal The Addyman Plesiosaur from Andamooka, "the finest known opalised skeleton on Earth"[30] The Burning of Troy, the now-lost opal presented to Joséphine de Beauharnais by Napoleon I of France and the first named opal[57] The Flame Queen Opal The Halley's Comet Opal, the world's largest uncut black opal Although the clock faces above the information stand in Grand Central Terminal in New York City are often said to be opal, they are in fact opalescent glass The Roebling Opal, Smithsonian Institution[58] The Galaxy Opal, listed as the "World's Largest Polished Opal" in the 1992 Guinness Book of Records[59] The Rainbow Virgin, "the finest crystal opal specimen ever unearthed"[60][61][62] Largest black opal in the world [63] The Fire of Australia, assumed to be "the finest uncut opal in existence"

Price: 15.98 USD

Location: Tucson, Arizona

End Time: 2024-09-11T01:42:58.000Z

Shipping Cost: 5.95 USD