It also has a high density, ranging from 3150 to 3530 kilograms per cubic metre (over three times the density of water) in natural diamonds and 3520 kg/m 3 in pure diamond. Tetrahedra are rigid, the bonds are strong, and of all known substances diamond has the greatest number of atoms per unit volume, which is why it is both the hardest and the least compressible. In diamond they are sp 3 and the atoms form tetrahedra with each bound to four nearest neighbors. In graphite the bonds are sp 2 orbital hybrids and the atoms form in planes, with each bound to three nearest neighbors 120 degrees apart. The two most common allotropes of pure carbon are diamond and graphite. Solid carbon comes in different forms known as allotropes depending on the type of chemical bond. Main article: Material properties of diamondĭiamond is a solid form of pure carbon with its atoms arranged in a crystal. Natural, synthetic and imitation diamonds are most commonly distinguished using optical techniques or thermal conductivity measurements. Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide. Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gases by chemical vapor deposition (CVD). Much more recently (hundreds to tens of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites. Under high pressure and temperature, carbon-containing fluids dissolved various minerals and replaced them with diamonds. Most were formed at depths between 150 and 250 kilometres (93 and 155 mi) in the Earth's mantle, although a few have come from as deep as 800 kilometres (500 mi). Most natural diamonds have ages between 1 billion and 3.5 billion years. Diamond also has a very high refractive index and a relatively high optical dispersion.

Small numbers of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (defects), green (radiation exposure), purple, pink, orange, or red. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.īecause the arrangement of atoms in diamond is extremely rigid, few types of impurity can contaminate it (two exceptions are boron and nitrogen). Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, but diamond is metastable and converts to it at a negligible rate under those conditions. Transparent to subtransparent to translucentĭiamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Less often blue, green, black, translucent white, pink, violet, orange, purple, and red. Typically yellow, brown, or gray to colorless. Its lustrous faces also indicate that this crystal is from a primary deposit. 'We think that lonsdaleite could be used to make tiny, ultra-hard machine parts if we can develop an industrial process that promotes replacement of pre-shaped graphite parts by lonsdaleite,' said Tomkins.The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. The material might be useful in mining or just for bragging rights about your wild hexagonal space bling. 'It's been estimated mathematically to be 58% harder than diamond, but that is yet to be proven by measurement.' 'We don't really know how hard lonsdaleite is,' Tomkins told CNET.

Tomkins says the space diamond sample provides a new process for industries to attempt to replicate. The study was led by Tomkins and published Monday in Proceedings of the National Academy of Sciences. Similar processes are used under controlled environments to produce materials for certain metals, semiconductors and other products. The team actually think this prevailing hypothesis of diamonds forming during the impact could be wrong - and the diamonds may have formed at lower pressures after the destruction. In lay-speak, that means the space diamonds were likely formed by carbon-based materials, potentially, on a dwarf planet being subject to extreme pressures after a cosmic traffic accident.

Diamond meteorite