What is a Diamond?

The mineral diamond is a crystalline form, or allotrope, of carbon (other allotropes of carbon include graphite and fullerene). It is one of the most known and most useful of more than 3,000 known minerals. Diamonds are renowned for their superlative physical qualities, especially their hardness and their high dispersion of light. These properties and others make diamond valued for use in jewelry and a variety of industrial applications. Most diamonds are mined from volcanic pipes, where they have been deposited by deep-origin volcanoes drawing material from over 90 miles (150 km) deep within the Earth, where the pressure and temperature is suitable for diamond formation. Most diamonds are mined in central and southern Africa, although significant deposits have also been discovered in Canada, Russia, Brazil, and Australia. About 130 million carats (26,000 kg) of diamonds are mined annually, with a total value of nearly $9 billion. In addition, nearly four times that mass is artificially produced as synthetic diamond. The gemological appeal of diamonds lies in their hardness and optical properties. Diamonds used as gems are cut and polished into a number of faceted shapes in order to accentuate these attractive qualities. The hardness of diamonds allows them to hold a polish extremely well and resist scratching (only other diamonds can scratch a diamond), giving excellent luster. The dispersion of white light into a rainbow of colors, known in the trade as fire, is the other primary characteristic of gem diamonds, and has been highly prized throughout history. Gem diamonds are commonly judged by the four Cs: carat, clarity, color, and cut. Diamonds have been treasured as gems since at least 2,500 years ago, when they were used in religious icons in India. Popularity of diamonds as gemstones increased starting in the 19th century as new cutting designs that display diamonds' gem qualities better were developed

How are Diamonds Formed?

Atoms are the basic structural units of all matter. Every mineral is defined by the types and relative quantities of its atoms. This is called chemical composition. It's also defined by the arrangement of its atoms-its structure-which is usually orderly and predictable.
Differences in chemical composition and structure give minerals their unique properties. Variations in either one can result in a very different mineral. For example, the atoms in a spinel (a type of colored stone) are arranged in ways similar to those in diamonds. But spinel is made up of different chemical elements.

A chemical element is a substance that consists of only one kind of atom. Most minerals are combinations of two or more elements. Colorless synthetic spinel, for example, looks a little like diamond at first glance. In fact it was once used in jewelry as a common diamond imitation. But it is made of three elements: magnesium, aluminium, and oxygen.

Diamond is the only gem made of a single element: carbon. Diamond is typically about 99.95 percent carbon. The other 0.05 percent can include one or more trace elements, which are atoms that aren't part of a diamond's essential chemistry. Some of them can influence its color or shape.

Formation conditions also help determine a mineral's identity. Diamond forms under high temperature and pressure conditions that exist only within a specific depth range beneath the earth's surface. Graphite, like diamond, contains only carbon, but its formation process is very different. The result is that graphite is very soft and brittle, while diamond is so hard that you can only scratch it with another diamond.
Without any one of these factors, diamond might be just another mineral. Fortunately, though, the magic combination of composition, structure, and formation gives diamonds the qualities that make them extraordinary.