Diamond

In mineralogy,diamond(from the ancient Greekαδάμας –adámas"unbreakable") is a metastable allotrope of carbon, where the carbon atomsare arranged in a variation of the face-centered cubiccrystal structure called a diamond lattice. Diamond is less stablethan graphite, but the conversion rate from diamond to graphite is negligible at standard conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bondingbetween its atoms. In particular, diamond has the highest hardnessand thermal conductivityof any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knivesand diamond anvil cells. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boronand nitrogen. Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown ( lattice defects), green (radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical dispersion(ability to disperse light of different colors). Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 118 mi) in the Earth's mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years (25% to 75% of the age of the Earth). Diamonds are brought close to the Earth's surface through deep volcanic eruptionsby a magma, which cools into igneous rocksknown as kimberlitesand lamproites. Diamonds can also be produced synthetically in a high-pressure high-temperatureprocess which approximately simulates the conditions in the Earth's mantle. An alternative, and completely different growth technique is chemical vapor deposition(CVD). Several non-diamond materials, which include cubic zirconiaand silicon carbideand are often called diamond simulants, resemble diamond in appearance and many properties. Special gemologicaltechniques have been developed to distinguish natural and synthetic diamondsand diamond simulants.Blog Directory at OnToplist.com