<P> Because of its extremely rigid lattice, diamond can be contaminated by very few types of impurities, such as boron and 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). </P> <P> Most natural diamonds have ages between 1 billion and 3.5 billion years . Most were formed at depths of 150 to 250 kilometers (93 to 155 mi) in the Earth's mantle, although a few have come from as deep as 800 kilometers (500 mi). Under high pressure and temperature, carbon - containing fluids dissolved minerals and replaced them with diamonds . Much more recently (tens to hundreds of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites . </P> <P> Diamonds can be produced synthetically in a high pressure, high temperature method (HPHT) 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 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 diamonds, synthetic diamonds, and diamond simulants . </P> <P> The name diamond is derived from the ancient Greek αδάμας (adámas), "proper", "unalterable", "unbreakable", "untamed", from ἀ - (a -), "un -" + δαμάω (damáō), "I overpower", "I tame". Diamonds are thought to have been first recognized and mined in India, where significant alluvial deposits of the stone could be found many centuries ago along the rivers Penner, Krishna and Godavari . Diamonds have been known in India for at least 3,000 years but most likely 6,000 years . </P>

Where are diamonds mostly found in the world