Diamond: queen of them all

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Named after the Greek 'adamas' meaning hard and untameable, the diamond is the hardest of all natural materials.

The gem is actually a form of carbon, like graphite; however, when crystallised, a diamond's atoms form a compact network securely bonded on all sides, giving it a tight, extremely-hard structure with a different atomic structure. Conversely, graphite's atoms are arranged in sheet form.

It is still unconfirmed as to where these carbon atoms come from; however, some scientists believe they are freed from gasses generated within magma chambers in the Earth's mantle, and are then carried towards each other by the convection currents in the magma. The magma then becomes the "womb" in which the diamonds grow.

Under the high pressures of the Earth's mantle, the magma may find a crack in the Earth's crust in which to fit. Once the magma cools, the diamond crystals and the magma rise to the surface, the latter forming kimberlite – named after the town of Kimberley in South Africa. This was where miners first dug for diamonds. Millions of years ago, towering kimberlite pipes spanned kilometres high.

Rough diamonds are categorised into five different grades: stones are evenly-shaped crystals; shapes are less evenly-shaped crystals; cleavages are broken or misshapen crystals; macles are triangular-shaped, twin crystals; flats are broken, glass-shaped crystals.

Each of these diamonds can be cut into gems. The diamond is celebrated for its incredible brilliance and dispersion of colour. The quality of the gem's scintillation (termed "adamantine") is dependent on how much light is reflected from its surface and inside. Around 17 per cent is reflected from the surface, while around 80 per cent is reflected from inside.

As tough as diamond is reputed to be, there are weaknesses in the bonds between the atoms in certain areas of the gem. These areas are called cleavage planes. If a diamond is hit in these areas, it will split. Cleavage planes can be quite useful, allowing the lapidary to shape a rough diamond into a good weight and shape.

Considered the most famous of gemstones, diamonds have taken pride of place in the hearts of many women throughout recent history. Largely as a result of clever marketing, the diamond is now renowned as "a girl's best friend" and has become the traditional stone used in engagement rings.

Diamonds are most common in a (white) clear colour, but are also available in a variety of fancy colours ranging from yellow and brown, to green, blue, pink and even red. The colour is due to impurities in the stone, the most common being nitrogen. For example, blue diamonds contain a minute trace of boron.

Naturally, the boldest colours in each category are considered the most valuable.

Mystically, diamonds were believed to hold many magical and medicinal properties. They were thought to calm the mentally ill and to ward off devils, phantoms and even nightmares. They were supposed to impart virtue, generosity and courage. During the middle ages it was believed a diamond could heal if the sick person took it to bed and warmed it with their body, breathed upon it while fasting or wore it next to the skin.

Birthstone for April, the popularity of the diamond is firmly entrenched in the modern market. Its versatility means it can be used to complement a range of jewellery settings, alongside almost any other gem and set in any metal.

fact sheet

Hardness: 10
Variety of: carbon
Found: India is the oldest source, but large supplies are presently found in Australia, Africa, USA, Brazil, Russia and Canada.