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Doublet (lapidary)
A doublet is a type of assembled gem composed in two sections. It is sometimes used to imitate other, more expensive gems. A garnet and glass doublet uses a top portion of natural garnet fused to any color of glass to imitate a gem. The color of glass used in the doublet is all that is seen, as the garnet provides no color. If seen in reflected light, a separation line may be seen. A harder garnet makes the stones more durable. In the case of opal Opal is a hydrated amorphous form of silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline form ... doublets, a backing layer of onyx or matrix (ironstone) gives the more fragile opal layer support and can make the opal look darker and higher quality. Garnet and glass doublets were first used around 1850 when it was noted that molten glass would adhere to garnet. It was a popular imi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Assembled Gem
An assembled gem (also called a composite gem) is a gemstone made up of other smaller gems. An assembled gem can often be a fake gem with a desirable piece of gemstone attached to pieces of inexpensive imitation gemstones. For example, a combination of a thin layer of green glass and a colorless piece of quartz would be a composite gem. Types A doublet is a type of assembled gem which is composed of two parts. A ''false doublet'' is a doublet which is a glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ... piece that looks like a real gem and a real gem that have been attached to look like a larger gem. A triplet is a type of assembled gem composed of three distinct parts. References Gemstones {{mineral-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opal Doublet
Opal is a hydrated amorphous form of silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered 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. The name ''opal'' is believed to be derived from the Sanskrit word (), which means 'jewel', and later the Greek derivative (), which means 'to see a change in color'. 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 pseudo chromatic 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Garnet
Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different species are pyrope, almandine, spessartine, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite. The garnets make up two solid solution series: pyrope-almandine-spessartine (pyralspite), with the composition range ; and uvarovite-grossular-andradite (ugrandite), with the composition range . Etymology The word ''garnet'' comes from the 14th-century Middle English word ''gernet'', meaning 'dark red'. It is borrowed from Old French ''grenate'' from Latin ''granatus,'' from ''granum'' ('grain, seed'). This is possibly a reference to ''mela granatum'' or even ''pomum granatum'' ('pomegranate', ''Punica granatum''), a plant whose fruits contain abundant and vivid red seed covers ( arils), whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda–lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term ''glass'', in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material. Despite bei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gemstone
A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, and obsidian) and occasionally organic materials that are not minerals (such as amber, jet, and pearl) are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their luster or other physical properties that have aesthetic value. Rarity and notoriety are other characteristics that lend value to gemstones. Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem expert is a gemologist, a gem maker is called a lapidarist or gemcutter; a diamond cutter is called a diamantaire. Characteristics and classification The traditional classification in the West, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opal
Opal is a hydrated amorphous form of silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered 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. The name ''opal'' is believed to be derived from the Sanskrit word (), which means 'jewel', and later the Greek derivative (), which means 'to see a change in color'. 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 pseudo chromatic 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 di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Onyx
Onyx primarily refers to the parallel banded variety of chalcedony, a silicate mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The colors of its bands range from black to almost every color. Commonly, specimens of onyx contain bands of black and/or white. Onyx, as a descriptive term, has also been applied to parallel banded varieties of alabaster, marble, calcite, obsidian and opal, and misleadingly to materials with contorted banding, such as "Cave Onyx" and "Mexican Onyx". Etymology ''Onyx'' comes through Latin (of the same spelling), from the Ancient Greek , meaning "claw" or "fingernail". Onyx with flesh-colored and white bands can sometimes resemble a fingernail. The English word "nail" is cognate with the Greek word. Varieties Onyx is formed of bands of chalcedony in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ironstone
Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be confused with native or telluric iron, which is very rare and found in metallic form, the term ''ironstone'' is customarily restricted to hard, coarsely banded, non-banded, and non-cherty sedimentary rocks of post-Precambrian age. The Precambrian deposits, which have a different origin, are generally known as banded iron formations. The iron minerals comprising ironstones can consist either of oxides, i.e. limonite, hematite, and magnetite; carbonates, i.e. siderite; silicates, i.e. chamosite; or some combination of these minerals.U.S. Bureau of Mines Staff (1996) ''Dictionary of Mining, Mineral, & Related Terms.'' Report SP-96-1, U.S. Department of Interior, U.S. Bureau of Mines, Washington, D.C.Neuendorf, K. K. E., J. P. Mehl Jr., and J. A. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
