Superhard materials

thumb|upright=1.25|The main ruby-producing countries

thumb|upright=1.25|Main sapphire-producing countries

Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock-forming mineral. It is a naturally 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: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange.

Graphene () is a variety of the element carbon which occurs naturally in small amounts. In graphene, the carbon forms a sheet of interlocked atoms as hexagons one carbon atom thick. The result resembles the face of a honeycomb. When many hundreds of graphene layers build up, they are called graphite.

chemical compound

chemical compound

chemical compound

Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice, as opposed to the cubical lattice of conventional diamond. It is found in nature in meteorite debris; when meteors containing graphite strike the Earth, the immense heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurs as microscopic crystals mixed in with ordinary diamon

compound of silicon and nitrogen

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a compound for coating metals

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chemical compound

type of composite material

thumb|Osmiridium-564562 Osmiridium and iridosmine are natural alloys of the elements osmium and iridium, with traces of other platinum-group metals.

chemical compound

nanocrystalline form of diamond

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chemical compound

thumb|Pressure-temperature diagram for various forms of silicon dioxide, including stishovite (at top left)

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chemical compound

chemical compound

Borazon is a brand name of a cubic form of boron nitride (cBN). Its color ranges from black to brown and gold. It is one of the hardest known materials, along with various forms of diamond and other kinds of boron nitride. Borazon is a crystal created by heating equal quantities of boron and nitrogen at temperatures greater than 1800 °C (3300 °F) at 7 GPa (1 million lbf/in2).

Adamant in classical mythology is an archaic form of diamond. In fact, the English word diamond is ultimately derived from adamas, via Late Latin and Old French . In ancient Greek (), genitive (), literally 'unconquerable, untameable'. In those days, the qualities of hard metal (probably steel) were attributed to it, and adamant became an independent concept as a result.

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type of material

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class of amorphous carbon material

Tantalcarbide is a rare mineral of tantalum carbide with formula TaC. With a molecular weight of 192.96 g/mol, its primary constituents are tantalum (93.78%) and carbon (6.22%), and has an isometric crystal system. It generally exhibits a bronze or brown to yellow color. On the Mohs hardness scale it registers as a 6–7. Tantalcarbide is generally found in a granular state. It is extremely dense at 14.6 g/cm^3. Sub-conchoidal fracturing is exhibited.

blue gemstone

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chemical compound

thumb|α-SiAlON parts SiAlON ceramics are a specialist class of high-temperature refractory materials, with high strength at ambient and high temperatures, good thermal shock resistance and exceptional resistance to wetting or corrosion by molten non-ferrous metals, compared to other refractory materials such as, for example, alumina. A typical use is with handling of molten aluminium. They also are exceptionally corrosion resistant and hence are also used in the chemical industry. SiAlONs also have high wear resistance, low thermal expansion and good oxidation resistance up to above ~1000&nbsp

chemical compound

chemical compound

chemical compound

high hardness element compounds of ruthenium and boron

Heterodiamond is a superhard material containing boron, carbon, and nitrogen (BCN). It is formed at high temperatures and high pressures, e.g., by application of an explosive shock wave to a mixture of diamond and cubic boron nitride (c-BN). The heterodiamond is a polycrystalline material coagulated with nano-crystallites and the fine powder is tinged with deep bluish black. The heterodiamond has both the high hardness of diamond and the excellent heat resistance of cubic BN. These characteristic properties are due to the diamond structure combined with the sp3 σ-bonds among carbon and the het