Why is diamond hard and graphite soft

A.Sabrianh asked recently why, as they’re both composed mainly from carbon, is diamond the hardest known surface while graphite is so soft

The answer lies in the bonding structure of their relevant carbon atoms. The crystal structure of a mineral defines its fundamental properties.

Q. What is so special about a diamond's carbon structure

A. In a carbon atom there are a certain number of parts (electrons) that are able to bond with electrons from adjacent carbon atoms. In a diamond every carbon electron bonds with all the electrons from its adjacent carbon atom. This repeated structure forms the strongest known chemical linkage, known as the covalent bond, which is responsible for many of diamond's special properties.

Whereas in graphite not all available electrons bond with the adjacent carbon atoms full compliment of available electrons. As a result, graphite is a much weaker substance.

Q. If diamond is so hard, how can it be cut so intricately

A. Although diamond is the hardest known chemical substance, it's possible to fracture it. Because of its particular crystal structure, diamond has certain planes of weaknesses along which it is possible to split it.

There are four different directions in which diamond will separate perfectly, known as cleavage. Diamond cutters take advantage of cleavage to fashion diamonds efficiently.

Q. Are all diamonds clear

A. No, diamonds can be pink, green, yellow or blue and even black.

Q. Where are diamonds formed

A. Deep within the Earth, up to 800km below the surface, where the conditions are perfect for heating and compacting the carbon atoms into diamonds. Diamonds form in rocks called eclogites and peridotites, which comprise the Earth's mantle.

Q. Where are diamonds found

A. At ground level, despite their subterranean origins. They are blasted to the surface, at the speed of sound by Kimberlitic eruptions. Kimberlite is the name of the lava which, in its

passing, rips the diamonds from their host rock and brings them up to the surface.

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by Lisa Cardy