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The hardness of synthetic diamond (70–150 GPa) is very dependent on the relative purity of the crystal itself. The more perfect the crystal structure, the harder the diamond becomes. It has been reported that HPHT single crystals and nanocrystalline diamond aggregates (aggregated diamond nanorods) can be harder than natural diamond. [25]
Mineralogical simulation predicts lonsdaleite to be 58% harder than diamond on the <100> face, and to resist indentation pressures of 152 GPa, whereas diamond would break at 97 GPa. [11] This is yet exceeded by IIa diamond's <111> tip hardness of 162 GPa.
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Its color ranges from black to brown and gold, depending on the chemical bond. 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/in 2).
It is a dense substance, with a density between 5.6 and 6.0 g/cm 3 —about 1.65 times that of diamond. Cubic zirconia is relatively hard, 8–8.5 on the Mohs scale—slightly harder than most semi-precious natural gems. [1] Its refractive index is high at 2.15–2.18 (compared to 2.42 for diamonds) and its luster is Adamantine lustre.
Its Vickers hardness (38 GPa), elastic modulus (460 GPa) [12] and fracture toughness (3.5 MPa·m 1/2) approach the corresponding values for diamond (1150 GPa and 5.3 MPa·m 1/2). [ 13 ] As of 2015 [update] , boron carbide is the third hardest substance known, after diamond and cubic boron nitride , earning it the nickname "black diamond".
The collision of a dwarf planet and an asteroid 4.5 billion years ago resulted in space diamonds in meteorites eventually landing on Earth.
Diamond (Mohs 10) is 1500 (off scale). Diamond was the hardest known naturally occurring mineral when the scale was designed, and defines the top of the scale, arbitrarily set at 10. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, or the softest material that can ...