Alumina (Aluminium Oxide) - The Different Types of Commercially Available Grades Alumina (Aluminium Oxide) - The Different Types of Commercially Available Grades Written by AZoMMay 3 2002 High Purity Aluminas Background Alumina is the most widely used oxide ceramic material. Its applications are widespread, and include spark plugs, tap washers, pump seals, electronic substrates, grinding media, abrasion resistant tiles, cutting tools, bioceramics, (hip-joints), body armour, laboratory ware and wear parts for the textile and paper industries. Very large tonnages are also used in the manufacture of monolithic and brick refractories. It is also used mixed with other materials such as flake graphite where even more severe applications are envisaged, such as pouring spouts and sliding gate valves. Key Properties The characteristics which alumina has and which are important for these applications are shown below.

• High compression strength • Resistant to chemical attack by a wide range of chemicals even at elevated temperatures • High thermal conductivity • High electrical resistivity even at elevated temperatures • Transparent to microwave radio frequencies • Low neutron cross section capture area • Raw material readily available and price not subject to violent fluctuation Annual Production Annual production of alumina is some 45 million tonnes, of which 90% is used in the manufacture of aluminium metal by electrolysis. Where Does Alumina Come From? Most of the aluminium oxide produced commercially is obtained by the calcination of aluminium hydroxide (frequently termed alumina trihydrate or ATH). The aluminium hydroxide is virtually all made by the Bayer Process. This involves the digestion of bauxite in caustic soda and the subsequent precipitation of aluminium hydroxide by the addition of fine seed crystals of aluminium hydroxide. Phases of Alumina Aluminium oxide exists in many forms, α, χ, η, δ, κ, θ, γ, ρ; these arise during the heat treatment of aluminium hydroxide or aluminium oxy hydroxide. The most thermodynamically stable form is α-aluminium oxide.

Aluminium Hydroxides Aluminium forms a range of hydroxides; some of these are well characterised crystalline compounds, whilst others are ill-defined amorphous compounds. The most common trihydroxides are gibbsite, bayerite and nordstrandite, whilst the more common oxide hydroxide forms are boehmite and diaspore. Commercially the most important form is gibbsite, although bayerite and boehmite are also manufactured on an industrial scale. Aluminium hydroxide has a wide range of uses, such as flame retardants in plastics and rubber, paper fillers and extenders, toothpaste filler, antacids, titania coating and as a feedstock for the manufacture of aluminium chemicals, e.g. aluminium sulfate, aluminium chlorides, poly aluminium chloride, aluminium nitrate. Commercial Grades of Alumina Smelter Grade Alumina Smelter or metallurgical grade alumina is the name given to alumina utilised in the manufacture of aluminium metal. Historically it was manufactured from aluminium hydroxide using rotary kilns but is now generally produced in fluid bed or fluid flash calciners.

In the fluid flash processes the aluminium hydroxide is fed into a counter-current stream of hot air obtained by burning fuel oil or gas. The first effect is that of removing the free water and this is followed by removal of the chemically combined water; this occurs over a range of temperatures between 180-600ºC. The dehydrated alumina is principally in the form of activated alumina and the surface area gradually decreases as the temperature rises towards 1000ºC. Further calcination at temperatures > 1000ºC converts this to the more stable α-form. The conversion to the α-form is typically of the order of 25% and the specific surface area is relatively high at >50m²/g due to the presence of transition aluminas. Calcined Alumina If aluminium hydroxide is heated to a temperature in excess of 1100ºC, then it passes through the transition phases of alumina referred to above. The final product, if a high enough temperature is used, is α-alumina. The manufacturing process is commercially undertaken in long rotary kilns.

Mineralisers are frequently added to catalyse the reaction and bring down the temperature at which the α-alumina phase forms; fluoride salts are the most commonly used mineralisers. These calcined alumina products are used in a wide range of ceramic and refractory applications. The main impurity present is sodium oxide. Various grades are produced which differ in crystallite size, morphology and chemical impurities. The calcined grades are often sub-divided into ordinary soda, medium soda (soda level 0.15-0.25% wt%) and low soda alumina. Low S oda Alumina Many applications, particularly in the electrical/electronic areas, require a low level of soda to be present in the alumina. A low soda alumina is generally defined as an alumina with soda content of <0.1% by weight. This can be manufactured by many different routes including acid washing, chlorine addition, boron addition, and utilisation of soda adsorbing compounds.

Reactive Alumina “Reactive” alumina is the terms normally given to a relatively high purity and small crystal size (<1 μm) alumina which sinters to a fully dense body at lower temperatures than low soda, medium-soda or ordinary-soda aluminas. These powders are normally supplied after intensive ball-milling which breaks up the agglomerates produced after calcination. They are utilised where exceptional strength, wear resistance, temperature resistance, surface finish or chemical inertness are required. Tabular Alumina Tabular alumina is recrystallised or sintered α-alumina, so called because its morphology consists of large, 50-500 μm, flat tablet-shaped crystals of corundum. It is produced by pelletising, extruding, or pressing calcined alumina into shapes and then heating these shapes to a temperature just under their fusion point, 1700-1850ºC in shaft kilns. After calcination, the spheres of shapes of sintered alumina can be used as they are for some applications, e.g. catalyst beds, or they can be crushed, screened and ground to produce a wide range of sizes.

As the material has been sintered it has an especially low porosity, high density, low permeability, good chemical inertness, high refractoriness and is especially suitable for refractory applications. Fused Alumina Fused alumina is made in electric arc furnaces by passing a current between vertical carbon electrodes. The heat generated melts the alumina. The furnace consists of a water cooled steel shell and 3-20 tonne batches of material are fused at any one time. The fused alumina has a high density, low porosity, low permeability and high refractoriness. As a result these characteristics, it is used in the manufacture of abrasives and refractories. High Purity Aluminas High purity aluminas are normally classified as those with a purity of 99.99% and can be manufactured by routes starting from Bayer hydrate using successive activations and washings, or via a chloride to achieve the necessary degree of purity. Even higher purities are manufactured by calcining ammonium aluminium sulfate or from aluminium metal. In the case of the route via ammonium aluminium sulfate, the necessary degree of purity is obtained by successive recrystallisations.

Especially high purities can be made from aluminium by reacting the metal with an alcohol, purifying the aluminium alkoxide by distillation, hydrolysing and the calcination. A minor route involves subjecting super purity aluminium metal pellets under distilled water to a spark discharge. Applications include the manufacture of synthetic gem stones such as rubies and yttrium aluminium garnets for lasers, and sapphires for instrument windows and lasers. Corundum structure - definition of Corundum structure by The Free Dictionary Corundum structure - definition of Corundum structure by The Free Dictionary Related to Corundum structure: 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: Sapphire| Birthstones | Gems | Geology & Soils | Data & Online Resources | SNR | UNL Share This Page Traditional Birthstones - Sapphire (September) If you were born in the month of September, sapphire is your birthstone. Sapphire is a variety of corundum or aluminum oxide and Al203 gives its chemical formula---that is, two parts of Aluminum to three parts of Oxygen. The axes are arranged in a hexagonal crystal, a crystal with four axes, three of which are of equal length and intersect at 60 degree angles, and one of which is unequal in length to the others and intersects the others at a right angle. Sapphire's companion variety of corundum is ruby. Rubies are red to orange-red to purplish red. If corundum is pink, the United States Federal Trade Commission requires that the stone be sold as a sapphire.

In the United States "pink rubies" are eliminated from the gem trade by legal definition. In the simplest terms, corundum that is any color other than red is a sapphire. Except for color, all of the other physical and optical properties of sapphire are identical to those of ruby and you are referred to the ruby page for these data. Supply and demand has dictated that cornflower blue sapphires are the most expensive. These stones are rare and the finest examples come from Kashmir, a mountainous area in northern India on the Pakistan border. Geographic isolation, political instability and high demand all combines to make these stones very expensive. Sapphires have been found in many other places in the world but few have attained the desirability of the Kashmir stones. In the United States, the Yogo Gulch area in Montana has historically produced some fine sapphires but few of these attain the size of the fine Kashmir gems. Labor and mining costs have been very high in the United States and the Yogo Gulch mines have generally not been profitable for the operators. Fee localities are areas where one can pay a set fee for the privilege to extract gems and minerals from mines or claims that are owned by a second party.

There are several such fee locality sapphire mines in Montana that have been profitable for both the mine owners and the prospectors who have chosen to pay the fee. The prospector pays a set fee for the right to extract a given weight or volume of sapphire bearing rock or gravel. The fee locality operators allow only the use of hand tools such as picks, shovels, crowbars, gads and wedges. The miner extracts the sapphire bearing rock with the larger tools. This material is sieved through a series of screens that allow the miner to separate and discard the extremely large cobbles as well as the very fine grained sand, silt and clay. The volume the miner pays for is actually only that that is in the size range that will produce the most useable stones. The sieved residue is placed in buckets and toward the end of the day the miners return to the base camp where the operators have electric shake tables that wash the gravel and concentrate the particles with high specific gravity toward the bottom of a pan. A half-ton of gravel may actually yield only a few pounds of sapphire bearing concentrate. When the concentrate is collected in the pan, the pan is removed from the shaker and is dumped over quickly on a flat table.

The largest sapphires will normally be on the top of the pile or what was earlier the bottom of the pan. Smaller stones may be found through the rest of the concentrate. In addition to sapphire being found in Montana, some stones have also been produced from mines in North Carolina where several fee localities exist. Alluvial gravel that covers much of the North American mid-continent has also produced an occasional sapphire for the lucky prospector. In the Old World sapphire has been found in alluvial gravel in Burma and Sri Lanka. Many of the colorless stones from Sri Lanka can be enhanced by heat treatment. There are many other localities of lesser importance throughout the world that have produced sapphires. Johnson and Coeval (1998, p. 293, 294), citing F. L. Southland and M. I. Garland stated that corundum formed in two distinct geochemical environments. (1) Alkali basalt where partial melting of the lithosphere over rising plumes of the earth's mantle can lead to eruptions of gem bearing lava. (2) Sapphires from Montana formed in crustal metamorphic sources on the basis of low Gallium contents.

Sapphire form in rocks that geologists call undersaturated, or rocks that have no free quartz. Spinel is another gem that forms in undersaturated rocks. Spinel may come in many of the same colors as sapphire and in earlier times many stones that were called sapphire or ruby included both corundum and spinel. Modern gem testing procedures can easily separate the two different minerals. The colors of sapphires and rubies are controlled by trace elements that are included in the crystal lattice in amounts usually not exceeding about three percent. Some of these are listed in the table below: Chromium Oxide, Cr203---ruby Titanium Oxide, TiO2 and Ferrous Iron Oxide, Fe203----blue Ferrous Iron Oxide---yellow Chromium Oxide, Ferrous Iron Oxide---orange Ferric Iron Oxide, Fe304 and Titanium Oxide---green Chromium Oxide, Ferrous Iron Oxide, Titanium Oxide---purple. For Further Reading Johnson, M. L., and Koivula, J. I., (editors) 1998. Colored Stones. In Gem News, Gems and Gemology, Winter, 1998, p. 293.

Liddicoat, R. T., 1969. Handbook of Gem Identification. Gemological Institute of America, Los Angeles, CA, 430 p. Schumann, W., 1977. Gemstones of the World. Sterling Publishing Co., New York, 256 p. Shipley, R. M., 1971. Dictionary of Gems and Gemology. Gemological Institute of America, Los Angeles, CA, 230 p. Zeitner, J. C., 1996. Gem and Lapidary Materials for Cutters, Collectors, and Jewelers. Geoscience Press, Tucson, AZ, 347 p. Sapphire crystals, Sri Lanka. 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 Sapphire (Al2O3) Growth speed is 1 to 4 cm/hour in Inert medium (argon). The method makes it possible to grow crystals of complicated shape.

Blanks (ribbons) 80 mm thick and 300 mm long can be produced. Stepanov (or EFG) method - a shaped growth technique used for growing sapphire in near-net finished shape, including tubes, rods, sheets, and fibers. This technique can also provide unique shapes and sealed assemblies. By Stepanov method, ribbon crystals up to 500 mm long and 80 mm wide are grown. Crystals grown by this method can have different crystallographic orientations (A, R, random) and are mainly used for industrial & mechanical applications, where good optical qualities are not important. Typical Sapphire applications: Sapphire substrates: · Blue LED's (BLED's) - sapphire is the substrate for the growth of III-V and II-VI compounds such as GaN for LED's, · for IR Detectors, for the growth of mercury cadmium tellurium (HgCdTe), GaAs wafer carriers, microwave integrated circuits Aerospace: · Sapphire is used for its durability and erosion/corrosion resistance, often in combination with the ability to withstand high heat while having a very broad transmission range.

Applications include: · Windows - FLIR (Forward Looking Infra Red) windows for sensors and other optics. Optical clarity over a broad spectral range combines with durability in this application. · Windows - for erosion resistance in salt and blowing sand environments, sapphire is used in conventional windows and dome shapes in replacement of softer, more fragile IR transmitting materials. · Countermeasures lamps - sapphire flash lamps are used in IRCM's (Infra red countermeasures). The high temperature performance of sapphire is combined with broad spectral range in this application. Analytical applications: · Sapphire is used in analytical applications where combinations of high temperature, pressure, and hydrofluoric acid species are encountered. These applications need the survivability of sapphire, while often needing other properties such as favourable UV (ultraviolet) or IR (infrared) transmission. · NMR (Nuclear Magnetic Resonance) tubes; Sapphire is used for very high-pressure applications in replacement of glass or quartz tubes. · Sample preparation - sapphire is used in digestion cells as sheaths and liners.

When hydrofluoric acid is used, sapphire replaces quartz components · Analytical chemistry - for mass spectroscopy, ICAP, and other systems, sapphire replaces quartware to improve durability and reduce contamination while offering good UV transmission. Medical applications: · Sapphire is used in surgical systems for laser transmission and in contact with bodily fluids. · Surgical tips - sapphire is used in contact tips for various surgical laser applications · Endoscope lenses - sapphire is often used in endoscope lenses due to its durability in contact with tissues and in sterilisation environments such as autoclaving · Sapphire knives - with a sapphire knife, thinner sections are possible. The near perfect cutting edge of this knife / blade gives distortion-free sections down to 10 microns thick. Optical applications: · Sapphire is used for short and long wavelength applications (UV and IR) beyond the range where conventional optics performs adequately. High temperatures and hostile environments also necessitate the use of sapphire optics. · Illumination windows - for very high brightness illumination, sapphire windows survive the very high heat while providing the broadest spectral transmission. · Sapphire lightguides - sapphire rods; used in high temperature thermometry beyond the range of quartz optics.

· Optical components: lenses, prisms and other laser and infrared optics are fabricated from high optical quality sapphire. Watch industry: Sapphire is widely used for watch glasses. The world demand in watch industry centres on scratchproof sapphire watch crystals. However, besides traditional flat shapes, crystals with spherical and cylindrical curves are also in great demand. Typical specifications: uses of corundum mineral uses of corundum mineral Corundum Mineral | Uses and Properties - GEOLOGY.COM The uses and properties of the mineral Corundum with photos by Geology.com Corundum Mineral,Aluminum Oxide,Natural Corundum,Corundum Mineral Uses Read about corundum, corundum mineral, natural corundum, corundum mineral uses, corundum information, corundum properties, corundum suppliers, corundum … Corundum: The mineral Corundum, Sapphire, Ruby info & pictures Detailed description, properties, and locality information guide about the mineral corundum: ruby and sapphire. Corundum - Wikipedia, the free encyclopedia Corundum is a crystalline form of aluminium oxide (Al 2 O 3) with traces of iron, titanium and chromium. It is a rock -forming mineral.

It is one of the naturally ... Corundum Factsheet and Information Page - … Corundum mineral information page at mineralminers.com: your on-line link for scientific facts and mineralogical information about natural corundum, with links to all ... CORUNDUM (Aluminum Oxide) - Amethyst Galleries' Mineral Gallery When someone lists the most famous gemstones such as diamond, topaz, aquamarine, emerald and garnet, corundum does not usually get mentioned. However, its two ... CORUNDUM TRADER | Trade Corundum and Semi Precious Stones Different Uses of Corundum Before starting to understand the different uses of corundum it is useful to understand the composition and origins of the mineral. Corundum Mineral Data - Mineralogy Database General Corundum Information : Chemical Formula: Al2O3 : Composition: Molecular Weight = 101.96 gm Aluminum 52.93 % Al 100.00 % Al 2 O 3 Corundum: Corundum mineral information and data.

Classification of Corundum: IMA status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered" Strunz 8th edition ID: 4/C.04-10: Nickel-Strunz 10th ... The Most Important Uses of the Mineral Sapphire | eHow 作者: Contributing Writer Sapphires are in the non-red corundum category of minerals and are considered the second hardest mineral on the Mohs scale. Sapphires are aluminum oxides that can … Uses of Corundum An informative article about the uses of corundum mineral and where it can be found. Mineral Properties, Uses and Descriptions Home » Minerals Mineral Uses, Properties, Descriptions. Popular Mineral Items: Mineral Information ... Uses of Corundum: Corundum is a very interesting mineral. Corundum Uses: Gemstones and Abrasives - Gemstones Advisor … Corundum Uses: Abrasives. The corundum mineral is commonly used as an abrasive. It is crushed to a powder of varying size depending on how rough the grinding stone, ...

corundum (mineral) -- Encyclopedia Britannica corundum, naturally occurring aluminum oxide mineral (Al 2 O 3) that is, after diamond, the hardest known natural substance. Its finer varieties are the gemstones ... Corundum Mineral Corundum is a common mineral found around the world in several forms such as red ruby and blue sapphire. Corundum mineral is popular in rock and mineral … uses of corundum mineral Besides the major material processing equipment, SBM Machinery also can provide our clients the indispensable accessory equipment such as excavator, dump truck ... Corundum - Oxide Minerals - About Geology - The Complete … Corundum is one of the oxide minerals. ... Corundum is the standard for hardness 9 in the Mohs hardness scale. This corundum crystal has a typical tapered shape and ... Uses of Corundum? - Ask.com Corundum is a natural mineral whose principle composition is aluminium oxide. Historically mined in the Middle East and India and used in grinding wheels, Corundum Common Uses of Corundum? - Ask.com Corundum is a mineral which is naturally clear in a crystalline form of aluminium oxide.

It is used as an abrasive because of its high hardness and it uses Emery Corundum | Define Corundum at Dictionary.com noun a common mineral, aluminum oxide, Al 2 O 3 , notable for its hardness: transparent varieties, as sapphire and ruby, are used as gems, other varieties as ... RUBY (variety of Corundum) - Amethyst Galleries' Mineral Gallery Ruby is the red variety of corundum, the second hardest natural mineral known to antiquity. The non-red variety of corundum is Sapphire. Sapphires are well known ... Corundum Mineral - Free Articles Directory | Submit Articles ... Corundum is the second hardest natural mineral known to science.The History SaysOne century ago, the richest corundum mine in the world was in Canada, at … Corundum main page - Home | The University of Texas at Austin C ORUNDUM Corundum is crystalline aluminum oxide, Al 2 O 3, second hardest on Mohs Scale, and one of the most popular (and expensive) of gem minerals.

Corundum - Wikipedia, the free encyclopedia Corundum is a crystalline form of aluminium oxide (Al 2 O 3) with traces of iron , titanium and chromium . It is a rock -forming mineral . It is one of the naturally ... Minerals | Corundum - PIRSA- Home This page contains a description of Corundum, what it is used for, where it is mined and other general information. Corundum - University of Wisconsin–Madison Corundum Mineral description. Corundum is an aluminum oxide mineral of the oxides and hydroxides group, with structural formula Al 2 O 3. The structure consists ... corundum Facts, information, pictures | Encyclopedia.com articles ... corundum Mineral, Al 2 O 3; sp. gr. 3.9–4.1; hardness 9; trigonal; the two main varieties blue and green, but can be yellow, or brown to almost black, and ... corundum - definition of corundum by the Free Online Dictionary ... co·run·dum (k-r n d m) n.

An extremely hard mineral, aluminum oxide, Al 2 O 3, sometimes containing iron, magnesia, or silica, that occurs in gem varieties such as ... Corundum - University of California, Berkeley normally use a mixed cut on the ... Heat Treatment of Corundum ... This may involve rupture of gas or fluid inclusions or partial dissolution of mineral inclusions. Corundum Uses - Ajilbab.Com Portal Discover Latest info about Corundum Uses pictures and Alumina Works, Nanoderm Acne Scar Treatment Scars Stretch Marks, ... Gypsum Mineral Sample For Rock Kits. Sapphire Mineral Information photos and Facts Corundum Sapphire Mineral Facts: Chemical Formula: Al 2 O 3 Corundum is nearly always a practically pure oxide of aluminum of the composition Al 2 O 3, in which there are 52.9 ... HowStuffWorks "Corundum" Corundum is a mineral that is studied in geology. Visit HowStuffWorks to learn more about the mineral corundum. Industrial Uses for Rubies | eHow Rubies are transparent red specimens of a mineral known as corundum.

Corundum is a type of aluminum oxide and is the second-hardest mineral in the world, after ... What On Earth Corundum | Earth Sciences Museum 200 University Avenue West. Waterloo, ON, Canada N2L 3G1. +1 519 888 4567 Corundum - 1911 Encyclopedia Britannica - Free Online CORUNDUM, a mineral composed of native alumina (Al203), remarkable for its hardness, and forming in its finer varieties a valuable gem-stone. Specimens were sent … Corundum: Corundum mineral information and data. Classification of Corundum: IMA status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered" Strunz 8th edition ID: 4/C.04-10: Nickel-Strunz 10th ... Corundum - Skyrim Wiki Guide - IGN - Video Games, Wikis, … Corundum is used more as an alloy to make advanced versions of other armors, such as banded-iron armor and plate armor. Corundum ore is smelted wit...

Corundum Sapphire - Interesting Facts - Susan Wong on HubPages Sapphire, means 'dear to the planet saturn' in Greek. It is a mineral known as corundum made from alumunium oxide. They are found either naturally or manufactured in ... Corundum | Learn everything there is to know about Corundum … corundum, mineral, aluminum oxide, Al 2 O 3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal ... corundum - Definition of corundum - Dictionary definitions you … a very hard mineral, aluminum oxide, AlO: a dark, coarse variety ( emery ) is used for grinding and polishing; clear, transparent varieties ( ruby, sapphire ) are ... About Stones of Corundum and Other Varieties of Rubies about gems and jewels of the mineral stone corundum including red rubies and their many varieties, and industrial uses for other colors of corundum Corundum is the form of mineral from which sapphires and rubies ... Corundum mineral is naturally clear, but can have different colors when impurities are present.

Transparent corundums are used as gems, and if they're red, then they ... Corundum - Definition and More from the Free Merriam-Webster ... Definition of CORUNDUM: a very hard mineral that consists of aluminum oxide occurring in massive and crystalline forms, that can be synthesized, and that is used for ... Uses Of Corundum, Uses Of Corundum Products, Uses Of Corundum ... Uses Of Corundum, You Can Buy Various ... Luoyang Refractory Mineral Co., Ltd. Contact Details. China (Mainland) Compare. High Al2O3 Density Corundum for … What are some uses of corundum? | Answers Encyclopedia: … Get the answer to "What are some uses of corundum?" ... Minerals, Mining, and Metallurgy; Planet Earth; Storms ; View all subjects at Answers Encyclopedia. Corundum | Ward's Science An extremely hard mineral and long an important industrial abrasive, Corundum also has many gem varieties. Ruby and sapphire are varieties of corundum colored by ... Minerals - Edkins Family Index Page Short descriptions and photographs of over a hundred different minerals and rocks. Projects for schools.

What is corundum used in - The Q&A wiki The overwhelming use, by far, of corundum is in the manufacture of abrasives--sandpaper, ... Rocks and Minerals; Science; Sedimentary Rock; Soil; Stalagmites … Corundum: Corundum mineral information and data. Classification of Corundum: IMA status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered" Strunz 8th edition ID: 4/C.04-10: Nickel-Strunz 10th ... The Most Important Uses of the Mineral Sapphire | eHow 作者: Contributing Writer Sapphires are in the non-red corundum category of minerals and are considered the second hardest mineral on the Mohs scale. Sapphires are aluminum oxides that can … Uses of Corundum An informative article about the uses of corundum mineral and where it can be found. Mineral Properties, Uses and Descriptions Home » Minerals Mineral Uses, Properties, Descriptions. Popular Mineral Items: Mineral Information ... Uses of Corundum: Corundum is a very interesting mineral.

Corundum Uses: Gemstones and Abrasives - Gemstones Advisor … Corundum Uses: Abrasives. The corundum mineral is commonly used as an abrasive. It is crushed to a powder of varying size depending on how rough the grinding stone, ... corundum (mineral) -- Encyclopedia Britannica corundum, naturally occurring aluminum oxide mineral (Al 2 O 3) that is, after diamond, the hardest known natural substance. Its finer varieties are the gemstones ... Corundum Mineral Corundum is a common mineral found around the world in several forms such as red ruby and blue sapphire. Corundum mineral is popular in rock and mineral … uses of corundum mineral Besides the major material processing equipment, SBM Machinery also can provide our clients the indispensable accessory equipment such as excavator, dump truck ... Corundum - Oxide Minerals - About Geology - The Complete … Corundum is one of the oxide minerals. ... Corundum is the standard for hardness 9 in the Mohs hardness scale. This corundum crystal has a typical tapered shape and ... Uses of Corundum? - Ask.com Corundum is a natural mineral whose principle composition is aluminium oxide.

Historically mined in the Middle East and India and used in grinding wheels, Corundum

Question: Which gem variety is an aluminium oxide with the formula Al203?
Answer: Sapphire