How are Diamonds Formed?

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 elemts.

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 immitation. 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 differen. 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.