Diamond Properties : Composition

Diamond is composed of the element carbon. Only nitrogen and boron are known with certainty to be incorporated in the diamond lattice.

Diamond is carbon in its most concentrated form. Except for trace impurities like boron and nitrogen, diamond is composed solely of carbon, the chemical element that is fundamental to all life.

But diamond is distinctly different from its close cousins the common mineral graphite and lonsdaleite, both of which are also composed of carbon. Why is diamond the hardest surface known while graphite is exceedingly soft? Why is diamond transparent while graphite is opaque and metallic black? What is it that makes diamond so unique?

The key to these questions lie in diamond's particular arrangement of carbon atoms or its crystal structure--the feature that defines any mineral's fundamental properties. A crystal is a solid body formed from the bonding of atomic elements or compounds in a repeating arrangement. Often, crystals possess smooth external faces. Due to their symmetrical and finite nature, the building blocks of crystals are limited to relatively small numbers of atoms, and their chemical compositions to simple numerical combinations of elements.

Major impurities:

• Nitrogen, up to 0.2% in natural Type Ia diamond.
• Nickel, iron, etc, up to 10% as inclusions in synthetic diamond (p.p.m. or less in natural diamond).
• Aluminium, up to 10 p.p.m in natural diamond. Boron, up to ~ 0.25p.p.m. in natural Type IIb and 270p.p.m. in specifically doped Type IIb synthetic diamond-now thought to be responsible for semiconducting properties of Type IIb diamond. Many other impurities are also believed to be present in the form of inclusions.
• Inclusions: Twenty-five mineral species have been positively identified

Other Properties of Diamond.