Osmium

Osmium is a hard but brittle metal that remains lustrous even at high temperatures. It has a very low compressibility. Correspondingly, its bulk modulus is extremely high, reported between 395 and 462 GPa  (gigapascals -kN/mm2), which rivals that of diamond (443 GPa). The hardness of osmium is moderately high at 4 GPa.Because of its hardness, brittleness, low vapor pressure (the lowest of the platinum group metals), and very high melting point (the fourth highest of all elements), solid osmium is difficult to machine, form, or work.Osmium has a blue-gray tint and is the densest stable element, slightly denser than iridium.Calculations of density from the X-ray diffraction data may produce the most reliable data for these elements, giving a value of 22.562±0.009 g/cm3 for iridium versus 22.587±0.009 g/cm3 for osmium.Osmium was discovered in 1803 by Smithson Tennant and William Hyde Wollaston in London, England.The discovery of osmium is intertwined with that of platinum and the other metals of the platinum group.Osmium (from Greek osme meaning "smell") is a chemical element with symbol Os and atomic number 76.  Its alloys with platinum, iridium, and other platinum group metals are employed in fountain pen nibs, electrical contacts, and other applications where extreme durability and hardness are needed.Osmium is the least abundant stable element in Earth's crust with an average mass fraction of 50 parts per trillion in the continental crust.Within Earth's crust, osmium, like iridium, is found at highest concentrations in three types of geologic structure: igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa,though the large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin in Canada are also significant sources of osmium. Smaller reserves can be found in the United States. Osmium tetroxide has been used in fingerprint detection and in staining fatty tissue for optical and electron microscopy. In 1898 an Austrian chemist, Auer von Welsbach, developed the Oslamp with a filament made of osmium, which he introduced commercially in 1902.The only known clinical use of osmium appears to be for synovectomy in arthritic patients in Scandinavia. It involves the local administration of osmium tetroxide (OsO4) which is a highly toxic compound. The lack of reports of long-term side effects suggest that osmium itself can be biocompatible, although this depends on the osmium compound administered. In 2011, osmium(VI)and osmium(II) compounds were reported to show anti cancer activity in vivo, it indicated a promising future for using osmium compounds as anti cancer drugs. Osmium is usually sold as a minimum 99.9% pure powder. Like other precious metals, it is measured by troy weight and by grams.

Its price in 2012 was about $400 per troy ounce (or about $13,000 per kilogram), depending on the quantity and its supplier.Osmium is one of the heaviest elements known; it is twice as heavy as lead and 22 times as heavy as water. It is also the least compressible material known. Osmium is a member of the platinum family of metals and is found in ores containing platinum. Osmium tetroxide, the most important osmium compound, is a powerful oxidizing agent. It is used to harden and stain microscope slides of biological specimens, and plays an important role in the synthesis of certain organic compounds, including cortisone. Osmium was discovered in 1804 by Smithson Tennant, a British chemist. Osmium metal remained as a residue when he dissolved crude platinum in aqua regia (a mixture of nitric and hydrochloric acids). 

The name osmium is derived from osme, the Greek word for smell, in recognition of the strong, chlorinelike odor of osmium tetroxide.osmium Symbol: Os. Atomic number: 76. Atomic weight: 190.2. Specific gravity: 22.57. Hardness: 7.0. Melting point: about 5,520 F. (3,050 C.). Boiling point: about 9,000 F. (5,000 C.). Osmium has seven stable isotopes: Os-184, Os-186 through 190, and Os-192. It belongs to Group VIII of the Periodic Table, and its principal valences are +3, +4, +6, and +8.A vest made of osmium would be extremely expensive, pricing in at around $100/gram.