Corundum sapphire

Hard Materials (7) Quartz, granite (8) topaz (9) corundum, sapphire, emeiy (10) diamond. 

Corundum Sapphire, rubv AI2O3 All but r 4.02 1.762-1.770 9 Conchoidal, some... 

AI2O3 Corundum, sapphire Growth in a variety of directions best growth in a cone of directions 60° from c 2040... 

Diamond is the hardest material known to man. The hardness of diamond on the Mohs hardness scale is 10. The second hardest material is corundum (sapphire [AI2O3]), which has a hardness of 9. Corundum, as well as diamond, is transparent to visible radiation. The real difference in hardness is quite large because the absolute hardness of diamond is 7,000 Knoop and of the corundum is 2,000 Knoop [24]. Bulk modulus of diamond is 4420 kbar [25] but is only 2400 kbar for synthetic sapphire. However, because the cost of sapphire is much lower than that of the diamond and also sapphire is more transparent to UV light, sapphire anvil cells (SAC) are often used for an optical cell for pressure <100 kbar. Sometimes cubic zirconia anvils are also used for pressure <30 kbar [26]. 

Schwartz and coworkers [489] also extended their CH3(CH2)i7P03H2 SAM studies to a new substrate as sapphire (corundum). Sapphire, undoped single crystal of q -A1203, is widely used as a substrate for thin-film deposition of metals, semiconductors, or insulators. Several crystallographic faces of sapphire are available, two of which have been studied, namely, C-face (1000) and R-face (1102). Different growth kinetics were observed for the two crystal orientations, which could be related to the surface energetics [489]. 

Rubies are the red gemstone of corundum sapphires can be blue, yellow, green, or violet. Only diamond is harder than rubies or sapphires. Rubies and sapphires are difficult to cut because they have no cleavs e and are brittle. Some of the most lamous rubies and sapphires are much more expensive per carat than diamonds. One of the most lamous sape phires is the Star of India (53 carats), and one of the most lamous rubies is the Edwrard ruby (167 carats). 

Although silicon carbide, carborundum, was first synthesized before the turn of the century, new syntheses and applications for this important compound are still being developed. The name carborundum derives from its hardness (9.3 on the Mohs hardness scale) and was coined to indicate that SiC falls between carbon (diamond = 10.0) and corundum (sapphire, AI2O3 = 9.0). 

Aluminium oxide occurs naturally as emery (an impure form) and as corundum. Corundum is a crystalline form which may be coloured by traces of impurity, for example as ruby (red) and sapphire (blue). Small synthetic rubies and sapphires have been made by heating alumina with the colouring oxide in an oxy-hydrogen flame. 

The compounds of greatest importance are aluminum oxide, the sulfate, and the soluble sulfate with potassium (alum). The oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glassmaking and refractories. Synthetic ruby and sapphire are used in lasers for producing coherent light. 

Aluminum oxide. Al3+ ions are present in corundum Heft), ruby (top right), and sapphire (bottom right). The anion in each case is 02-. 

A colorless mineral known as corundum (composed of aluminum oxide) is colorless. A red variety of corundum known as ruby, a precious stone, owes its color to impurities of chromium within the crystal structure of corundum. Blue and violet varieties of corundum are classified as sapphires, the blue being the result of iron and titanium impurities, and the violet of vanadium impurities within the corundum crystal structure. Another colorless mineral is beryl (composed of beryllium aluminum silicate) but blue aquamarine, green emerald, and pink morganite, are precious varieties of beryl including different impurities aquamarine includes iron, emerald chromium and vanadium, and morganite manganese. 

Ruby and Sapphire. Ruby and sapphire are "sister stones" both are gemstone forms of the mineral corundum (composed of aluminum oxide). Pure corundum is colorless, but a variety of trace elements cause corundum to exhibit different colors. Ruby is red corundum, while sapphire is corundum in all colors except red. The red in rubies is caused by trace amounts of chromium the more intense the red color of a ruby, the more chromium it contains. The blue in sapphires is caused by titanium and/or iron impurities (Garland 2002 Hughes 1997). 

Occurs in nature in abundance the principal forms are bauxites and lat-erites. The mineral corundum is used to produce precious gems, such as ruhy and sapphire. Activated aluminas are used extensively as adsorbents because of their affinity for water and other polar molecules and as catalysts because of their large surface area and appropriate pore sturcture. As adsorbents, they are used for drying gases and liquids and in adsorption chromatography. Catalytic properties may be attributed to the presence of surface active sites (primarily OFT, 02, and AF+ ions). Such catalytic applications include sulfur recovery from H2S (Clauss catalysis) dehydration of alcohols, isomerization of olefins and as a catalyst support in petroleum refining. 

Oxides Brucite Mg(OFl)2, corundum AI2O3, ruby AI2O3, sapphire AI2O3... 

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, corundum, and quartz families. Quartz has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spind are produced commercially in over 100 colors (2). Synthetic cubic zirconia has been made in essentially all colors of the spectrum (11), but only the colorless diamond imitation is produced commercially in any quantity. 

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