Corundum is a crystalline form of aluminium oxide containing traces of iron, titanium and chromium. It is a rock-forming mineral, it is a transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: sapphire. Rubies are red due to the presence of chromium, sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange; the name "corundum" is derived from the Tamil-Dravidian word kurundam. Because of corundum's hardness, it can scratch every other mineral, it is used as an abrasive on everything from sandpaper to large tools used in machining metals and wood. Some emery is a mix of corundum and other substances, the mix is less abrasive, with an average Mohs hardness of 8.0. In addition to its hardness, corundum has a density of 4.02 g/cm3, unusually high for a transparent mineral composed of the low-atomic mass elements aluminium and oxygen.
Corundum occurs as a mineral in mica schist and some marbles in metamorphic terranes. It 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, it occurs as a detrital mineral in stream and beach sands because of its hardness and resistance to weathering. The largest documented single crystal of corundum measured about 65 cm × 40 cm × 40 cm, weighed 152 kg; the record has since been surpassed by certain synthetic boules. Corundum for abrasives is mined in Zimbabwe, Afghanistan, Sri Lanka, India, it was mined from deposits associated with dunites in North Carolina, US and from a nepheline syenite in Craigmont, Ontario. Emery-grade corundum is found on the Greek island of Naxos and near Peekskill, New York, US. Abrasive corundum is synthetically manufactured from bauxite. Four corundum axes dating back to 2500 BCE from the Liangzhou culture have been discovered in China.
In 1837, Marc Antoine Gaudin made the first synthetic rubies by reacting alumina at a high temperature with a small amount of chromium as a pigment. In 1847, Ebelmen made white synthetic sapphires by reacting alumina in boric acid. In 1877 Frenic and Freil made crystal corundum from. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little chromium at temperatures above 2,000 °C. In 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process; the Verneuil process allows the production of flawless single-crystal sapphire and ruby gems of much larger size than found in nature. It is possible to grow gem-quality synthetic corundum by flux-growth and hydrothermal synthesis; because of the simplicity of the methods involved in corundum synthesis, large quantities of these crystals have become available on the market causing a significant reduction of price in recent years. Apart from ornamental uses, synthetic corundum is used to produce mechanical parts, scratch-resistant optics, scratch-resistant watch crystals, instrument windows for satellites and spacecraft, laser components.
For example, the KAGRA gravitational wave detector's main mirrors are 23 kg sapphires, Advanced LIGO considered 40 kg sapphire mirrors. Corundum crystallizes with trigonal symmetry in the space group R3c and has the lattice parameters a= 4.75 Å and c= 12.982 Å at standard conditions. The unit cell contains six formula units; the toughness of corundum is sensitive to surface crystallographic orientation. It may be 6–7 MPa·m1⁄2 for synthetic crystals, around 4 MPa·m1⁄2 for natural. In the lattice of corundum, the oxygen atoms form a distorted hexagonal close packing, in which two-thirds of the gaps between the octahedra are occupied by aluminium ions
By-elections to the 10th Canadian Parliament were held to elect members of the House of Commons of Canada between the 1904 federal election and the 1908 federal election. The Liberal Party of Canada led a majority government for the 10th Canadian Parliament; the list includes Ministerial by-elections which occurred due to the requirement that Members of Parliament recontest their seats upon being appointed to Cabinet. These by-elections were always uncontested; this requirement was abolished in 1931. Alberta and Saskatchewan entered Confederation in 1905. Unlike in the case of other provinces that joined after 1867, the new provinces were represented by ridings drawn for the Northwest Territories, the members elected in 1904 continued to sit as representatives of the old NWT ridings, except where they resigned as indicated below. List of federal by-elections in Canada Parliament of Canada–Elected in By-Elections
Lawrence "Larry" Schneider, is a Canadian politician. Born in Regina, Saskatchewan, he was mayor of Regina from 1979 until 1988. In the 1988 federal election, he was elected as a Progressive Conservative candidate in the riding of Regina—Wascana. Under Kim Campbell's government, from June 25, 1993 until November 3, 1993, he was Minister of Western Economic Diversification, he lost his seat in the 1993 election to Ralph Goodale. He was president of the Prairie Implement Manufacturers' Association. Schneider supported Conservative Party candidate Michael Kram in the riding of Regina-Wascana in the 2015 federal election. Notes Sources Larry Schneider – Parliament of Canada biography