Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (lattice defects), green, purple, pink, orange or red.
Diamond also has relatively high optical dispersion, that is ability to disperse light of different colors, which results in its characteristic luster.
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).
In particular, nanocrystalline diamond aggregates were measured to be harder than any large single crystal diamond.
Diamond has a hardness of 10 (hardest) on this scale.The difference is that in diamonds, the bonds form an inflexible three-dimensional lattice.In graphite, the atoms are tightly bonded into sheets, which can slide easily over one another.In the 20th century, experts in gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.Four characteristics, known informally as the ) that crystallizes into the diamond lattice which is a variation of the face centered cubic structure.