In mineralogy, diamond (from the ancient Greek αδάμας – adámas "unbreakable") is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells.

Diamond has remarkable optical characteristics. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boron and nitrogen. Combined with wide transparency, this results in the clear, colorless appearance of most natural diamonds. 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), which results in its characteristic luster. Excellent optical and mechanical properties, combined with efficient marketing, make diamond the most popular gemstone.

Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 120 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 eruptions by a magma, which cools into igneous rocks known as kimberlites and lamproites. Diamonds can also be produced synthetically in a high-pressure high-temperature process which approximately simulates the conditions in the Earth mantle. An alternative, and completely different growth technique is chemical vapor deposition (CVD). Several non-diamond materials, which include cubic zirconia and silicon carbide and are often called diamond simulants, resemble diamond in appearance and many properties. Special gemological techniques have been developed to distinguish natural and synthetic diamonds and diamond simulants.

Read more about Diamond:  History, Material Properties, Industry

Famous quotes containing the word diamond:

    I met Jack Kennedy in November, 1946.... We went out on a double date and it turned out to be a fair evening for me. I seduced a girl who would have been bored by a diamond as big as the Ritz.
    Norman Mailer (b. 1923)

    The lover never sees personal resemblances in his mistress to her kindred or to others. His friends find in her a likeness to her mother, or her sisters, or to persons not of her blood. The lover sees no resemblance except to summer evenings and diamond mornings, to rainbows and the song of birds.
    Ralph Waldo Emerson (1803–1882)

    Masts in the offing wagged their tops;
    The swinging waves pealed on the shore;
    The saffron beach, all diamond drops
    And beads of surge, prolonged the roar.
    John Davidson (1857–1909)