Ruby | All About Gemstones at Juwelo “The Ruby not only stands in the very foremost class of coloured gems, but it occupies among precious stones in general a position which is unquestionably supreme.” Edwin Streeter, Precious Stones and Gems (1898) Etymology Ruby derives from the Latin ‘ruber’ (red). While many red gems were called ‘Ruby’ until the development of scientific gemology in the 18th century, during antiquity, Ruby, Garnet, Spinel and other red gemstones were collectively called ‘carbunculus’ (‘little coal’ in Latin). Known as ‘anthrax’ (live coal) to the ancient Greeks, these gemstones were beautiful deep red gems that became the color of glowing coal embers of a fire when held up to the sun. Chemical composition of Ruby Ruby and Sapphire are color varieties of the mineral Corundum (crystalline aluminum oxide), which derives its name from the Sanskrit word for Rubies and Sapphires, ‘kuruvinda.' Corundum produces ‘allochromatic’ gemstones, meaning that trace amounts of elements such as chromium, iron and titanium as well as color centers are responsible for producing its rainbow of colors.

Ruby owes its red colors to chrome, while a brown hue is imparted by the presence of iron. Sapphires also present orange and red hues (such as the Sunset Sapphire), but these hues do not match the color spectrum assigned to Ruby red. Therefore, if Corundum reds are labeled ‘Ruby’, other colors are termed ‘Sapphire,' Even pure Ruby is only 80% red, however, also displays shades of orange, bright pink, purple and violet. Star Ruby Ruby extraction Rubies from Sri Lanka were used by the Ancient Greeks and Romans from about 480 B.C., making Sri Lanka the most ancient source of this gem, even though the ‘classic’ Ruby originates in the Mogok Valley of central Myanmar. Today, Ruby is also extracted in Möng Hsu in northwest Myanmar. This country, thanks to the presence of classically colored and highly transparent stones, is considered one of the best sources of Rubies in the world, and its name is so intrinsically linked to this gemstone that its kings were known as ‘Ruby Lords.' Other sources of Ruby include Afghanistan, Cambodia, China, India, Kenya, Madagascar, Mozambique, Pakistan, Sri Lanka, Tanzania, Thailand and Vietnam.

AAA Tanzania Ruby The history of Ruby Beloved by the Indians as ‘Ratnaraj’, King of Gems, July’s birthstone represents passion, love and romance. Ancient Indians believed Ruby to possess an internal fire that would endow a long life, while in the middle ages, Rubies, like so many other gems, were believed to possess prophetic powers, deepening in color if bad moons were rising. Worn by the Burmese as a talisman to protect against illness, misfortune or injury, Rubies were once known as ‘blood drops from the heart of mother earth.' In the 19th century, Ralph Waldo Emerson penned a poem, describing Ruby as “drops of frozen wine from Eden’s vats that run." Properties of Ruby Ruby is one of the most expensive and better-known gemstones, and is far rarer than Diamonds, particularly the most intense and pure red examples. Particularly fine and transparent examples may be classified as AAA quality.

As a diochroic (two-colored: purplish red and orangey red) pleochroic gemstone, even the ‘finest’ Ruby is still going to be only around 80 percent pure red, with secondary splashes of orange, pink, purple and violet. Clear rubies without inclusions are virtually non-existent. As is the case for Alexandrite and Emerald, chrome is responsible for the inclusions in Ruby. While both Ruby and Sapphires are classed as Type II gemstones (gems that typically grow with some minor inclusions in nature that may be eye-visible), Rubies are usually more included and smaller. Fine microscopic rutile inclusions (called ‘silk’) in some Rubies can actually softly distribute light, boosting both beauty and value. Most Rubies look best when exposed to natural or white light, and many display a strong glowing electric red fluorescence. A ‘waterfall’ of Rubies Varieties of Ruby Clear rubies without inclusions are virtually non-existent. As is the case for Alexandrite and Emerald, chrome is responsible for the inclusions in Ruby.

While both Ruby and Sapphires are classified as Type II gemstones (gems that typically grow with some minor inclusions in nature that may be eye-visible), Rubies are usually more included and smaller. Fine microscopic Rutile inclusions (called ‘silk’) in some Rubies can actually softly distribute light, boosting both beauty and value. Most Rubies looks best exposed to natural or white light, and many display a strong glowing electric red fluorescence. Ruby displays a clear and obvious star, with straight and equidistant rays. The standard calls for a six pointed star, but rare examples with twelve rays have also been found. All Star Rubies and Cat's Eye Rubies are cut in cabochon (a convex, highly polished but unfaceted shape), and their optical phenomenon is even more visible when exposed to a single, direct ray of light. The intense red of Malawi Ruby Care for Ruby Ruby may be subjected to normal cleaning, including steam or ultrasound cleaning. This gemstone may have voids, cavities, fissures and/or open fissures, which may increase the gemstone’s sensitivity to damage due to heat or some solvents.

Shopping with Juwelo Diverse selection to choose from Toll-Free Number Previously available only in Europe Secured by Aluminum Oxide Gemstones and Minerals | Gem5.com December Aluminum Oxide Gemstones & Minerals The following is a list of Aluminum Oxide gems and minerals listed in our database. Click the pictures to get full data, click the X to remove the gem from the list. Heliodor Beryl: Heliodor is a gem variety of Beryl with golden-yellow or light yellow-green color. In many cases heliodor is also used to include gems known as Golden beryl/ Golden emerald, though not to be confused with gold beryl. It is sometimes hard to establish a dividing line between heliodor and golden beryl. Its main characteristic is its color, which is the yellow-green of olive oil. Its pigment is uran ( read full ) Rutile: Rutile with anatase and brookite is a trimorph of titanium oxide in the Rutile group. It forms characteristic slender prismatic striated lengthways, variably terminated and often geniculate twinned crystals of the tetragonal system. Elbow- and heart-shaped (geniculated) twin crystals are common.

It is hard, heavy, fragile, with perfect cleavage. It has a metallic to adamantine lustre an ( read full ) Plasma Chalcedony: Plasma is a massive, semitransparent, leek to dark green variety of Chalcedony (a microcrystalline variety of the Quartz group), microgranular or microfibrous, consisting of speckles of red or brownish-red jasper, resembling drops of blood. It is translucent to opaque, may be dark green to bright-green, apple-green, or nearly emerald-green, containing microfibrous of actinolite, frequently fleck ( read full ) Spinel: Spinel is an extensive group of minerals in which magnesium may be replaced with iron, zinc, and above all, manganese. The hardness and fine colors of gem quality spinel, known as Noble Spinel, set it apart as a gem material from other types of spinel. It normally occurs as distinct octahedral crystals, as clusters also of octahedral habit, or as characteristic twins. The crystals are often iso ( read full ) Taaffeite: Taaffeite is a very rare beryllium magnesium aluminum mineral.

No other mineral has both beryllium and magnesium in its composition. It is one of the few gems to be discovered as a faceted stone instead of a rough, as most gemstones are. Rarely cut as a gem, taaffeite looks like a mauve-colored spinel, and its absorption spectrum is similar to it. But gemologists know they've found taaffeite when ( read full ) Padparadscha: Padparadschah is the name given to the orange-yellow sapphire, a gem variety of Corundum. It is also differentiated from the yellow sapphire, and is one of the rarest varieties of corundum. The main sapphire-bearing rocks are marble, basalt, or pegmatite. It is mined mainly from alluvial deposits or deposits formed by weathering, rarely from the primary rock. It usually occurs in placer deposit ( read full ) Hematite: Hematite is considered the most important Iron Ore mineral. Its crystals appear as reasonably thick. They may be tabular, or rhombohedral, and occasionally prismatic or pyramidal.

Tabular crystals may form as rosettes, when they are called "iron roses." It also occurs as massive, compact, columnar, fibrous, reniform, botryoidal, stalactitic, foliated, and granular. When hematite forms in a renif ( read full ) Sard: Sard is the uniformly colored red-brown or brownish-yellow variety of Chalcedony, which in turn is a microcrystalline variety of Quartz. There is no strict separation between sard and cornelian/carnelian (red to reddish brown), because they are both chalcedonies found in the same deposits and were employed for the same objects. The tints of a sard stone may be reddish or orange. Good-quality mat ( read full ) Fire Agate: Fire Agate is a term applied to much of the variety of chalcedony that occurs as botryoidal, consisting of crystals of minute platy inclusion of an iron mineral goethite or limonite minerals over the layers of chalcedony, producing a vivid rainbow containing every color in the spectrum, an iridescent, fire-like appearance, with careful polishing away of the brown outside layers.

When polished, it ( read full ) Cassiterite: Cassiterite may form as short or slender prismatic, or bipyramidal, elbow-shaped crystals. It has a crystal surface reflecting light as in a mirror. They may occur as massive, granular, botryoidal, and reniform. When found in granular, banded, fibrous masses, it looks like wood. When found in groups of large bright crystals, it is usually called "diamond tin." A red variety cut for collectors is k ( read full ) Ruby: Ruby is the most valuable variety of Corundum. The color varies from fiery vermilion to violet red, but because rubies are pleochroic, different colors are also found in the same stone; bright or sometimes brick red in one direction, tending to carmine in the other. The color is also accompanied by marked fluorescence which is stimulated by ordinary, artificial light, and above all, by the ultra ( read full ) Sapphire: Sapphire is the blue variety of Corundum.

Sapphires can be a very dark blue, to the point of seeming dense and blackish from a distance, sometimes accompanied by a blue to dull green pleochroism, which is only visible from the side in cut stones. They may also be a strong, but not too bright blue, easily recognizable from a distance, this being the real color. Other possibilities are light, usual ( read full ) Dumortierite: Dumortierite is a variety of gemstone of basic aluminum borosilicate with an orthorhombic crystal system. It appears usually in columnar or fibrous, radiating aggregates, sometimes reddish brown, dark blue, violet-blue. On the rare occasions that dumortierite forms crystals, they are prismatic. Faceted or prismatic blue or violet samples are rare, due to scarcity of individual crystals. It is ( read full ) Nephrite: Nephrite is a silicate of calcium, magnesium, and iron, containing fluorine and hydroxyl. It is an amphibole of the actinolite series. It occurs in all colors, also striped and spotted, but the most valuable color is green.

The amphiboles of the tremolite-actinolite series usually occur as elongated, parallel, radiating, or even fibrous crystals; but the variety known as nephrite has a very compa ( read full ) Rhodonite: Rhodonite is a silicate of manganese-iron-magnesium, a mineral of the Pyroxene group, with a triclinic crystal system. It appears as rare tabular crystals, sometimes with rounded edges and wrinkled faces. It sometimes occurs as distinct, translucent to semiopaque crystals, but more often it is in compact, granular, ot crystalline masses of a patchy, pink, flesh red or brownish red color, often wi ( read full ) Petalite: Petalite is a lithium aluminum silicate that is an important ore of lithium. This mineral forms, rarely, as small crystals, which are commonly twinned. More often, petalite forms as large, cleavable masses. It may be white, grey, pinkish, yellow, or colorless. It is transparent to translucent, with a vitreous to pearly luster, and fuses with difficulty.

It forms in very coarse-grained, acid igne ( read full ) Jadeite: Jadeite is a silicate of sodium and aluminum, and is a member of the Clinopyroxene group of minerals. It is so called because it is the source of one of the ornamental materials commonly known as Jade. It has a monoclinic crystal system, and occurs as granular aggregates of small crystals, but has occasionally been found in crystals of a few centimeters. The color varies a great deal because of t ( read full ) Grossular Garnet: Grossular is a nesosilicate in the Garnet group, with an isometric crystal system. Together with uvarovite and andradite, the three are known as the "ugrandite garnets," an isomorphous series of calcium garnet minerals.

It appears with dodecahedral or trapezohedral crystals of various colors; normally characterized by a green color, but also may be colorless, pale green or milky when pure, cinnam ( read full ) Kyanite: Kyanite is an aluminum silicate that occurs as elongated and tabular in groups of light-blue crystals darker toward the center, or flat, bladed crystals in schists and gneisses, or as radiating rosettes in quartz. It is trimorphous with sillimanite and andalusite. Kyanite is also known as disthene, meaning, "double strength." This refers to the fact that the hardness along the length of kyanite c ( read full ) Sinhalite: Sinhalite is a magnesium aluminum borate, and is most commonly found as transparent honey-yellow to brown grains or pebbles with an orthorhombic crystal system. It also appears as pale yellowish, yellow, brown, greenish-brown to black. It occurs in contact metamorphic rocks that are rich in boron, among gneiss or granite where limestones are being replaced through contact with magmatic rock.

But ( read full ) Orthoclase: Orthoclase mineral is a silicate of potassium and aluminum, belonging to the Feldspar group. It has the same composition as microcline, but is stable at slightly higher temperatures. It occurs as prismatic, sometimes flat-sided crystals, but in rocks it is usually anhedral. It may be perfectly transparent and yellow or almost colorless, but it is more often semi-opaque and white to grayish-white, ( read full ) Kornerupine: Kornerupine is a rare magnesium aluminum borate silicate which occurs as transparent prismatic crystals of the orthorhombic system. It is hard and a has good cleavage in one direction. Colours include a characteristic dark green leaning to brown and a rare and attractive bright vanadium green. This pleochroic colours are brown to greenish brown. Chatoyant stones show a bright eye against a dark g ( read full ) Turquoise: Turquoise is a hydrated phosphate of copper and aluminum in the Phosphates, Arsenates, Vanadates group, with a triclinic crystal system. It rarely occurs as prismatic crystals.

It is usually found as light-blue or green masses, nodules, and veins, sometimes filling cavities in various rocks. When it occurs as thin strips, it is tighter and brightly-colored at the center, lighter and porous on the ( read full ) Euclase: Euclase is a silicate with a monoclinic crystal system. It is considered a very rare gem of light blue color. It appears as long or short prismatic crystals, flattened and transparent. It is colorless, white, green, or blue, commonly a pale aquamarine or green, but crystals of a very fine dark blue (from iron) have been found at the Miami mine in Zimbabwe. Crystals are often striated. It ( read full ) Hauyne: Hauyne is a blue feldspathoid rock-forming mineral, one of four members of the sodalite mineral group that is a component of lapis lazuli. The other three are lazurite, sodalite, and nosean. It is a complex mineral of sodium, calcium, aluminum silicate, and sulfate.

Hauyne forms very bright and attractive though uncommon transparent blue dodecahedral or pseudo-octahedral crystals of the cubic sy ( read full ) Coral: Corals are the supporting framework of small polyps. Each coral polyp, a tiny marine animal that lives in enormous colonies, extracts calcium carbonate from the sea and exudes it through their bases to build a protective home around and above itself. Each generation of polyps dies in its protective home and each succeeding generation builds on top of its predecessor. They precipitate calcareous m ( read full ) Staurolite: Staurolite is a hydrous magnesium aluminum silicate that crystallizes in the monoclinic system. It appears as coarse, dark gold-brown prisms, or sometimes reddish-brown to black stubby crystals. On weathered rock, it stands out in contrast like sand-coated yellowish brown prisms. Surfaces are often rough or covered with an earthy coating because of natural alteration. It frequently occurs in ch ( read full ) Sillimanite: Sillimanite is a grayish-blue aluminum silicate with an orthorhombic crystal system. It is trimorphic with andalusite and kyanite.

All three have the same chemical compound but their atoms each arrange to create three different crystal forms. It appears as long, slender crystals without distinct terminations, in off-white, gray, brown, pale green, slate-blue, blue-green, and these crystals are of ( read full ) Brazilianite: Brazilianite is a soft and brittle mineral that in general does work very well as a gemstone. It's soft at 5.5 Mohs, and so it will quickly either shear apart, or crumble at the edges. As one might guess Brazilianite was first discovered in Brazil. It tends to be a yellow or light yellowish green mineral. This mineral has also been found in New Hampshire, United States. The mineral is so rare it ( read full ) Spessartine: Spessartine is the manganese-aluminum variety of Garnet, belonging to its sub-group of aluminum garnets. Garnets are a group of silicate minerals that all crystallize in the isometric system and have the same chemical formula, but in a diversity of proportions, so garnets show up as different varieties, in a broad range of environments.

Spessartine possesses the form typical of garnet crystals, w ( read full ) Iolite: Iolite is the violet-colored variety of Cordierite (named after French geologist P. Cordier), a silicate of aluminum and magnesium, with an orthorhombic crystal system. Though the name cordierite is used by mineralogists, the name iolite has become established among gemologists. It appears as stubby, prismatic crystals, pesudo-hexagonal twins with a glassy appearance. It is frequently microgranul ( read full ) Amblygonite: Amblygonite is a not so popular gem whose greek name means crooked. It comes in green, clear, yellow, and even purple. Older cut specimens may have slightly rounded facet edges due to the gems lack hardness (6 of 10). Amblygonite can be found in Brazil, France, the United States, Burma, and even Sweden. It may be confused easily with Brazilianite. ( read full ) Unarovite: Uvarovite is a rare, calcium-chromium emerald-green variety of Garnet.

Together with grossular (calcium-aluminum) and andradite (calcium-iron), it makes up the series of ugrandite garnets. These three have similar crystal structure and form, but just have different chemical proportions. It occurs in mixed crystals, so there is a partial replacement of some elements by others. It stands out from t ( read full ) Spodumene: Spodumene is a lithium aluminum silicate that crystallizes in the monoclinic system. It is one of several rock-forming minerals in the Pyroxene group, which are physically-related as their chemical content is quite similar and forms a chain. Fellow pyroxenes are jadeite, enstatite, diopside, hypersthene, augite, acmite, hedenbergite, pigeonite, and aegirineaugite. It appears as prismatic crystals ( read full ) Rubellite Tourmaline: Rubellite is the pink to red variety of Tourmaline, which is a complex borosilicate of aluminum and alkali, with iron, magnesium, and other cations.

It is found as fine acicular crystals in rocks, or as large individual crystals grown upon matrix where they may reach a weight of several kilograms. Most form elongated and striated trigonal (three-sided) prisms and these are terminated with trigona ( read full ) Sodalite: Sodalite is a sodium aluminum silicate chloride in the Sodalite group with an isometric crystal system. Its royal blue forms are the best known. As a mineral, it is a principal component of lapis lazuli. It appears very rare as dodecahedrons, crystals with 12 faces, but usually it shows as compact masses, bright blue, white or gray with green tints. It is unsaturated and rarely appears with inclu ( read full ) Lazulite: Lazulite is a compact, pleochroitic mineral which forms a series to scorzalite. It is dichroic, with a monoclinic crystal system. It appears as pointed, pseudo-dipyramidal, bright blue crystals in microgranular masses. It is hard, medium heavy, fragile with indistinct prismatic cleavage. It is translucent, with vitreous luster.

It is infusible, discolors and breaks into small fragments when heat ( read full ) Vesuvianite: Vesuvianite is a hydrous calcium magnesium aluminum silicate with a tetragonal crystal system. It is the preferred name used by mineralogists for all transparent varieties of Idocrase, the name used by gemmologists. It is a gem mineral that appears in diverse colors, and thus is prized by collectors. A compact green variety of vesuvianite that looks like jade is known as californite. A greenish-b ( read full ) Dravite: Dravite also called Brown Tourmaline is a sodium magnesium-rich mineral in the Tourmaline group of silicates, with a hexagonal system. Other members of this group include elbaite (sodium lithium aluminum rich); schorl and buergerite (sodium iron rich); uvite (calcium magnesium rich); and liddicoatite (calcium lithium aluminum rich).

A continuous solid solution series exists between uvite and dravi ( read full ) Zoisite: Zoisite is a hydrous calcium aluminum silicate in the Epidote group, with an orthorhombic crystal system, three crystal axes at right angles to each other, all of varying lengths. It appears in elongated, prismatic crystals, with fine parallel lines on the prism faces and usually poorly terminated. It also appears frequently in formless grains, poorly-defined crystals, rodlike aggregates and gran ( read full ) Pyrope: Pyrope is the iron magnesium and aluminum silicate of the pyrope-almandine series in the Pyralspite group of the Garnet family. Its beautiful deep-red gem quality makes it one of the most popular. Pure pyrope is colorless, but its red color, sometimes very bright, is due to small quantities of chrome in the crystal structure. It appears as dodecahedral or trapezohedral crystals, dark red, usually ( read full ) Goshenite Beryl: Goshenite is a colorless sodium-rich gem variety of Beryl, a group which includes Emerald and Aquamarine.

Other gem beryls include Heliodor and Morganite. It also appears are pale-green, apple-green, to bluish. All beryls are resistant to chemicals with the exception of fluoric acid. They are brittle and therefore easily damaged by knocks, have a vitreous luster, and occur with aquamarine. Their ( read full ) Microcline: Microcline is a silicate of potassium and aluminum, and an alkali member of the feldspar group. It is the phase of this compound that is stable at low temperature. The feldspars are major constituents of the rocks on the earth's crust and comprise some of the most important rock-forming minerals. The four feldspars - orthoclase, sanidine, microcline and anorthoclase - comprise a group called the ( read full ) Topaz: The transparent, colored crystals, which also have good luster, are widely used as gems. Topaz is a silicate of aluminum containing fluorine and hydroxyl which occurs in a variety of delicate colors, nicely added by impurities. It is often found in short to long crystal prisms with pyramid-shaped ends, or just clean finished edges.

It is often white, semiopaque, milky, or a faded yellow, ( read full ) Morganite: Morganite is a pale red-purple, rose, salmon to purplish red, slightly pink, cesium-bearing variety of Beryl. The Beryl group of silicates includes the important gem varieties emerald, blue aquamarine, pink morganite, and red and yellow beryl. The color of morganite is usually a soft pink without any overtones. It has glassy luster, like other beryls, but its pleochroism is not noticeable. The p ( read full ) Tugtupite: Tugtupite is a mineral closely related to sodalite and hackmanite, all cyclosilicates whose structural silicate tetrahedrons are arranged in rings. It is also called beryllosodalite and reindeer stone, and crystallizes in the tetragonal system. It is found in fine-grained aggregates of crystals with its own distinctive cyclamen colour.

Crystals are very small, tetragonal, almost cubic, or as shor ( read full ) Epidote: Epidote is widespread, forms a continuous series of minerals, ending with clinozoisite, which contains no iron. It occurs as crystals elongated and often striated parallel to length, and also as massive, fibrous, or granular habits. Epidote has a yellow-green color, ranges from yellowish-greenish to greenish-black. It has vitreous luster, and is transparent to nearly opaque. It has one perfe ( read full ) Hessonite: Hessonite is the brown-orange variety of Grossular, a nesosilicate in the Garnet group, with an isometric crystal system. It appears with dodecahedral or trapezohedral crystals, cinnamon-brown to orange because of its iron content. Its color matches that of the oil of cinnamon. It also appears as golden-yellow, yellow-brown, or reddish-brown. It is very hard, heavy, fragile, has no cleavage.

It ( read full ) Scapolite: Scapolite is a mixed crystal series, a complicated sodium calcium aluminum silicate group composed of calcium-rich meionite, and sodium-rich marialite. It appears as yellow, blue, pink, violet, or colorless prismatic crystals with a tetragonal system, mostly surface-growing, with perfect cleavage. These crystals are usually in aggregates that are massive granular, long columnar, dense, with vitr ( read full ) Tektites: Tektites are glass specimens rich in silica that many believed were actually meteorites. But, the locations in which tektites have been found, and their chemistry, led scientists to suggest that they may not in fact have come from outside planet Earth. Another conjecture is that tektites are formed from rocks that melted after being hit by a meteorite. Tektites actually have a composition not unl ( read full ) Moonstone: The variety name Moonstone is usually used to describe an optical effect and unlike most variety names it is not confined to a single species (The term is also applied to albite-moonstone, microcline-moonstone, labradorite-moonstone).

But Moonstone most prominently refers to the orthoclase feldspar, Adularia Moonstone, a microperthitic association of orthoclase and albite) and rarely to Albite M ( read full ) Zircon: Zircon is a zirconium silicate with a tetragonal crystal system, and also contains thorium and uranium. It appears as stubby, prismatic, isolated or sometimes dipyramidal, like two pyramids connected at their bases; or in twins, colorless to yellow, red, brown, gray or green, in irregular granules. It is very hard, heavy, with indistinct cleavage, and shell-like fracture. It is sometimes perfect ( read full ) Search Sapphires | Article about Sapphires by The Free Dictionary Sapphires | Article about Sapphires by The Free Dictionary Also found in: Dictionary , Thesaurus , Wikipedia . sapphire, precious stone. A transparent blue corundum corundum , mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in masses.

It is transparent to opaque and has a vitreous to adamantine luster. ..... Click the link for more information. , it is classified among the most valuable of gems. Sapphires are found chiefly in Thailand, India, Sri Lanka, and Myanmar and also in Australia and in the United States (in Montana). The sapphires from Kashmir are of a beautiful cornflower blue and are highly valued. The Sri Lankan varieties are paler; those from Montana have a metallic luster; and the Australian sapphires are of a dark blue shade approaching black. The terms yellow sapphire, purple sapphire, and green sapphire are used alternatively with Oriental topaz, Oriental amethyst, and Oriental emerald for other varieties of corundum. Like rubies of similar structure, some sapphires display a six-pointed star when cut to a cabochon (round-topped) shape and exposed to direct sunlight. Such star sapphires are usually obtained from Sri Lanka. Synthetic sapphires are made by the fusion of aluminum oxide, with titanium oxide added as a coloring agent.

Sapphire a variety of the mineral corundum (A1203), characterized by its dark or light blue color, which is caused by the simultaneous presence of the impurities Ti and Fe. Sapphire is a precious stone of order I. Star sapphire is characterized by as-terism in the form of a six-rayed star, which is brought about by microinclusions of rutile. Sapphire deposits are mainly placers and usually contain rubies. Sapphires are found in the Southern Urals in the USSR and in Thailand, Sri Lanka, and India. Synthetic sapphires that are used in the jewelry industry are obtained in the same manner as corundum. White sapphire is a synthetic colorless corundum that contains less than 0.001 percent impurities and has many specific physical properties that make it very useful in microelectronics, quantum electronics, high-resolution optics, and audio-optics. REFERENCE Corundum - definition of corundum by The Free Dictionary Corundum - definition of corundum by The Free Dictionary Related to corundum: Artificial Corundum co·run·dum (kə-rŭn′dəm) n.

An extremely hard mineral, aluminum oxide, Al2O3, sometimes containing iron, magnesia, or silica, that occurs in gem varieties such as ruby and sapphire and in a common black, brown, or blue form used chiefly in abrasives. [Tamil kuruntam.] (kəˈrʌndəm) n (Minerals) a white, grey, blue, green, red, yellow, or brown mineral, found in metamorphosed shales and limestones, in veins, and in some igneous rocks. It is used as an abrasive and as gemstone; the red variety is ruby, the blue is sapphire. Composition: aluminium oxide. Formula: Al2O3. Crystal structure: hexagonal (rhombohedral) [C18: from Tamil kuruntam; related to Sanskrit kuruvinda ruby] co•run•dum (kəˈrʌn dəm) n. a mineral, aluminum oxide, Al2O3, noted for its hardness: transparent varieties, as sapphire and ruby, are used as gems, other varieties as abrasives: often made synthetically.

[1720–30; < Tamil kuruntam; akin to Skt kuruvinda ruby] co·run·dum (kə-rŭn′dəm) An extremely hard mineral composed mainly of aluminum oxide. It occurs in gem varieties such as ruby and sapphire and in a dark-colored variety that is used for polishing and scraping. Corundum is the mineral used to represent a hardness of 9 on the Mohs scale. ThesaurusAntonymsRelated WordsSynonymsLegend: Corundum: The mineral Corundum, Sapphire, Ruby info & pictures Advertising Information The Mineral corundum Corundum is best known for its gem varieties, Ruby and Sapphire. Ruby and Sapphire are scientifically the same mineral, but just differ in color. Ruby is the red variety, and Sapphire is the variety that encompasses all other colors, although the most popular and valued color of Sapphire is blue. Sapphire is also only used to describe the gem variety; otherwise it is simply called Corundum. Corundum is a very hard, tough, and stable mineral. For all practical purposes, it is the hardest mineral after Diamond , making it the second hardest mineral. It is also unaffected by acid s and most environments.

Translucent brown Corundum and Emery are the most common forms of Corundum. These are fairly common forms, and due to their great hardness and prevalence are the most favorable abrasive s. The industrial term "emery" describing Corundum abrasives is derived from the variety Emery which is mined specifically for its use as an abrasive. Erosion may cause Emery to crumble and form sand, which are sometimes called "black sands." Corundum is easily synthesized , and many Corundum abrasives are synthetic. Synthetic gems are also easily created by adding traces of certain color producing elements to the Corundum solution, and letting the solution solidify into a boule , or synthetic, unprocessed "mineral" with a particular shape. This process is called the Verneuil process . Natural Ruby and Sapphire gemstone s may have their color artificially enhanced or deepened through heat treatment when used as gems. Some dark blue stones from certain localities may also be made a bright blue desirable color. USES Ruby and Sapphire are the most famous gemstones after Diamond . They have retained their high value throughout the centuries and are continuously and vigorously mined throughout the world.

Red rubies and blue Sapphires are the most popular Corundum gemstones, though other Sapphire colors such as orange, yellow, and green are becoming increasingly popular in gemstone use. Corundum has some electrical uses, and non gem material, such as Emery , is used as an abrasive because of its high hardness . The gemstone applications of the Corundum varieties are discussed in greater detail in their own dedicated gemstones pages. Make sure to also see the gemstone section on Ruby and Sapphire . NOTEWORTHY LOCALITIES The area of Mogok, Burma (Myanmar) is the source of some of the best gem -quality Ruby . Another significant Burmese deposit is Mong Hsu, which is currently a major Ruby producer, though its color isn't as fine as the Mogok material. Sri Lanka, especially the area of Ratnapura, Bibile, and Rakwana, is an excellent source of gem quality Corundum of all colors. The finest and largest crystallized specimens and aggregate s of gem-quality Sapphire are from Sri Lanka. Ruby with a brownish tint comes from Thailand, in the Chantaburi District.

Fine gem Ruby and Sapphire comes from Luc Yen, Yenbai Province, Vietnam; the Hunza Valley, Gilgit, Pakistan; and Jegdalek, Sorobi District, Afghanistan. Gem quality Sapphire is well-known at Pailin, Cambodia. Translucent to opaque Ruby, sometimes with asterism , is very abundant at Mysore (Mysuru) and Subramanium, in Karnataka, India. Africa has recently become a significant producer of Corundum, especially in Madagascar, where it is found in the Zazafotsy Quarry, Ambahatraso; and in Andranondambo, Amboasary District. A famous African locality in which opaque rubies are found in green Zoisite is is in Longido, Kilimanjaro Region, Tanzania. Another important Tanzanian Ruby mine is Winza, in Arusha. In the U.S., the Yogo Gulch in Judith Basin Co. has produced choice, deep blue Sapphire crystals. Not far from the Yogo Gulch, near Helena, waterworn Sapphires stones are found in the Missouri River throughout its length in Lewis and Clark County.

Montana is also the claim to a few other localities: the Gallatin Gateway and Salesville, Gallatin Co.; Rock Creek, Granite Co.; and Cottonwood Creek, Deer Lodge Co. In California, well-formed, elongated Corundum crystals were found in Cascade Canyon in the San Gabriel Mountains, San Bernardino Co. A well known Ruby locality is the Cowee Creek District, Macon Co., North Carolina, especially the area of Franklin. Large deposits of Emery were once worked near Peekskill, Westchester Co., New York; and Chester, Hampden Co., Massachusetts. An important Canadian occurrence of Corundum is the Burgess Mine, Bancroft, Hastings Co., Ontario. corundum - definition and meaning corundum Definitions from The American Heritage® Dictionary of the English Language, 4th Edition n. An extremely hard mineral, aluminum oxide, Al2O3, sometimes containing iron, magnesia, or silica, that occurs in gem varieties such as ruby and sapphire and in a common black, brown, or blue form used chiefly in abrasives. from Wiktionary, Creative Commons Attribution/Share-Alike License n.

An extremely hard mineral, a form of aluminum oxide with the chemical formula Al2O3, that occurs in the form of the gemstones sapphire and ruby; it is used as an abrasive. from the GNU version of the Collaborative International Dictionary of English n. The mineral alumina (Al2O3), as found native in a crystalline state. Transparent varieties are used as gemstones, including sapphire, which is the fine blue variety; the oriental ruby, or red sapphire; the oriental amethyst, or purple sapphire; and adamantine spar, the hair-brown variety. It is the hardest substance found native, next to the diamond. from The Century Dictionary and Cyclopedia n. Alumina, or the oxid of the metal aluminium, as found native in a crystalline state. from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved. n. very hard mineral used as an abrasive Etymologies from The American Heritage® Dictionary of the English Language, 4th Edition Tamil kuruntam. from Wiktionary, Creative Commons Attribution/Share-Alike License From Tamil குருந்தம் (kuruntam, "ruby").

Examples Aluminum oxide, when it occurs in crystals rather than on pans, makes up the abrasive called corundum, and is also the principal material of rubies and sapphires the gem colors come from chromium and titanium impurities. Sapphire | Article about sapphire by The Free Dictionary Sapphire | Article about sapphire by The Free Dictionary sapphire, precious stone. A transparent blue corundum corundum , mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in masses. It is transparent to opaque and has a vitreous to adamantine luster. ..... Click the link for more information. , it is classified among the most valuable of gems. Sapphires are found chiefly in Thailand, India, Sri Lanka, and Myanmar and also in Australia and in the United States (in Montana). The sapphires from Kashmir are of a beautiful cornflower blue and are highly valued. The Sri Lankan varieties are paler; those from Montana have a metallic luster; and the Australian sapphires are of a dark blue shade approaching black.

The terms yellow sapphire, purple sapphire, and green sapphire are used alternatively with Oriental topaz, Oriental amethyst, and Oriental emerald for other varieties of corundum. Like rubies of similar structure, some sapphires display a six-pointed star when cut to a cabochon (round-topped) shape and exposed to direct sunlight. Such star sapphires are usually obtained from Sri Lanka. Synthetic sapphires are made by the fusion of aluminum oxide, with titanium oxide added as a coloring agent. Sapphire a variety of the mineral corundum (A1203), characterized by its dark or light blue color, which is caused by the simultaneous presence of the impurities Ti and Fe. Sapphire is a precious stone of order I. Star sapphire is characterized by as-terism in the form of a six-rayed star, which is brought about by microinclusions of rutile. Sapphire deposits are mainly placers and usually contain rubies. Sapphires are found in the Southern Urals in the USSR and in Thailand, Sri Lanka, and India. Synthetic sapphires that are used in the jewelry industry are obtained in the same manner as corundum.

White sapphire is a synthetic colorless corundum that contains less than 0.001 percent impurities and has many specific physical properties that make it very useful in microelectronics, quantum electronics, high-resolution optics, and audio-optics. REFERENCE sapphire | gemstone | Britannica.com Sapphire jewelry Sapphire, transparent to translucent, natural or synthetic variety of corundum (aluminum oxide , Al2 O 3) that has been highly prized as a gemstone since about 800 bc. Its colour is due mainly to the presence of small amounts of iron and titanium and normally ranges from a very pale blue to deep indigo, with the most valued a medium-deep cornflower blue. Colourless, gray, yellow, pale pink, orange, green, violet, and brown varieties of gem corundum also are known as sapphire; red varieties are called ruby . Much sapphire is unevenly coloured; it is also dichroic; that is, the colour of most varieties changes with the direction of view. Alexandrite sapphire appears blue in daylight and reddish or violet in artificial illumination, somewhat like true alexandrite.

Careful heating and cooling under various conditions can induce permanent colour changes in sapphire (e.g., from yellow to colourless or greenish blue and from violet to pink). Other colour changes result from exposure to intense radiation. Most sapphire contains abundant microscopic inclusions; reflections from these yield a faint whitish sheen, known as silk. Tiny, regularly arranged mineral inclusions (commonly rutile) and elongate cavities are responsible for the asterism shown by star sapphire. Blue sapphire, natural specimen © Erica and Harold Van Pelt Photographers Sapphire is a primary constituent of many igneous rocks, especially syenites, pegmatites, and various basic (silica-poor) types; it also occurs in schists and metamorphosed carbonate rocks. Most commercial production has come from alluvial gravels and other placer deposits, where the sapphire commonly is associated with ruby and other gem minerals. The best known sources, including some lode deposits, are in Sri Lanka , Myanmar (Burma), Thailand , Australia (Victoria, Queensland, New South Wales), India , Madagascar , Russia, South Africa , and the United States (Montana, North Carolina). Most transparent sapphire is faceted, generally in the brilliant style.

Such gems have considerable sparkle, but they exhibit little fire because of their modest dispersion (separation of light into its component colours). Skillful cutting of unevenly coloured stones yields gems with a uniform appearance derived from only small portions of relatively deep colour. Star sapphire and other nontransparent varieties are cut en cabochon (in convex form, highly polished) rather than faceted. Despite its great hardness , some sapphire is carved or engraved, especially in the Orient. Similar Topics Corundum | P.G.I. Pune Gemological Institute P.G.I. Pune Gemological Institute Color : Brown to gray, less often red, blue, white,or yellow. Chemical formula : Aluminium oxide, Al2O3 Crystal system : Trigonal Major varieties : Ruby, Sapphire, Pink Sapphire, Violet Sapphire, Yellow Sapphire, Green Sapphire, Colourless Sapphire, Star Rubies and Sapphires. Different Coloured Asteriated The name corundum probably derived from the Sanskrit "kuruvinda" meaning "ruby". In India a pinkish-orange sapphire is called padparadscha and a pink light-red sapphire is called patmaraga.

Due to corundum's hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral, leaving behind a streak of white on the other mineral. It is commonly used as an abrasive, on everything from sandpaper to large machines used in machining metals, plastics and wood. Some emery is a mix of corundum and other substances, and the mix is less abrasive, with a lower average Mohs hardness near 8.0. In addition to its hardness, corundum is unusual for its high density of 4.02 g/cm³, which is very high for a transparent mineral composed of the low atomic mass elements aluminium and oxygen. Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. It also occurs in low silica igneous syenite and nepheline syenite intrusives. Other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals in pegmatites. Because of its hardness and resistance to weathering, it commonly occurs as a detrital mineral in stream and beach sands.

The largest documented single crystal of corundum measured ~65x40x40 cm3. Corundum for abrasives is mined in Zimbabwe, Russia, and India. Historically it was mined from deposits associated with dunites in North Carolina and from a nepheline syenite in Craigmont, Ontario. Emery grade corundum is found on the Greek island of Naxos and near Peekskill, New York. Abrasive corundum is synthetically manufactured from bauxite. Ruby A ruby is a pink to blood-red gemstone, a variety of the mineral corundum (aluminum oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from rubber, Latin for red. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the emerald, and the diamond. Blue Sapphire Color in gemstones breaks down into three components: hue, saturation, and tone. Hue is most commonly understood as the "color" of the gemstone.

Saturation refers to the vividness or brightness or "colorfulness" of the hue, and tone is the lightness to darkness of the hue. [3] Blue sapphire exists in various mixtures of its primary and secondary hues, various tonal levels (shades) and at various levels of saturation (brightness): the primary hue must, of course, be blue. Pink Sapphire This is the name given to the pink variety of corundum. Pink sapphire and ruby are regarded as 2 different varieties, despite the fact that the only difference is their depth in color. Pink sapphire’s most striking characteristics is its luster, common to all corundum and most noticeable in light colored specimens. Like all forms of corundum pink sapphire has a very good luster. It is normally given a mixed, oval cut and sometimes has fine inclusions and liquid veils in lacelike formations. Violet Sapphire It is formally known as “oriental amethyst” on account of its color. When the color of the sapphire tends to be blue-violet, red violet or pink violet, it is fairly distinctive, but not so when it is a true violet or violet with a slight hint of red.

Violet sapphires are easily distinguished, however, by their physical characteristics. If the density is measured with a heavy liquid such as methylene iodide, corundum rapidly sinks, while amethystine quartz floats. Yellow Sapphire Yellow sapphire may occur in quite a wide range of colors, from pale to canary yellow, gold, honey, and brownish yellow .The lighter, brighter colors are the most common. Medium-size or large stones are often seen, generally with a mixed ova cut having a rather large pavilion (to increase a depth of color). Green Sapphire In the 19th century green sapphire was known as “oriental emerald”. Due to its iron content, green sapphire is generally quite a strong, bright green color, sometimes with green to bluish green or yellowish green pleochroism. Green sapphire comes mainly from Australia but it is also found in the United States and Thailand. Colourless Sapphire When the crystal structure of corundum does not contain trace elements that act as colorants, it is completely clear, although this form is the least known in the gem market. It is perfectly colorless or occasionally has a slight yellow tinge and has the typical luster of corundum.

It is given a round (or almost round) mixed cut, or a slightly modified brilliant cut, having mainly been used as a substitute for diamond. Star Rubies and Sapphires The most striking phenomenon of rubies and sapphires is the development of the six ray star, arranged in perfect symmetry, which shifts its center as the stone is moved. It is clearly visible under a single light source such as the sun or a lamp. Such stones are invariably given a round or oval cabochon cut.

Question: Of which aluminium oxide mineral are ruby and sapphire among the coloured varieties?
Answer: Corundum