Diamond is by far the world's most popular gemstone and is well known to be the hardest naturally occurring material. It has the top rating of 10 on the Mohs Scale of Hardness, meaning that it is more resistant to scratching than any other natural gem material.
Made from pure carbon, diamond forms in the Earth's mantle at depths of around 100 miles. It is brought nearer to the surface through extreme volcanic activity and the movement of the Earth's plates. Diamond can often be found in distinctive geological formations called kimberlite pipes.
Diamond is the birthstone for April. The name is derived from the ancient Greek word "adamas", which means "unalterable" or "unbreakable" and it was the Greeks who considered diamonds to be the tears of the gods. The Romans believed that Cupid's arrows had tips made of diamonds to pierce any heart.
Over the centuries, diamonds have had many healing properties associated with them, such as being able to counter depression, reduce fevers and cure skin diseases.
The most popular diamonds have traditionally been colourless/white. However, diamond also comes in many "fancy" colours, such as yellow, brown (often known as champagne or cognac diamonds), blue, red, pink, purple, black and green. Some of these colours (particularly blue and red) are extremely highly valued.
Diamonds are normally classified using the 4Cs system - colour, clarity, cut and carat weight. The value of a colourless diamond is highly dependent on the "fire" (sparkle) of the stone
The top diamond-producing countries include Botswana, Russia, Canada, Australia and the Democratic Republic of Congo, although diamonds are also found in many other locations, particularly in Africa.
Synthetic (man-made) diamonds are a cheaper and increasingly popular alternative to their natural ccounterpart. The two main methods for creating diamonds in a laboratory are HPHT (high pressure, high temperature) and CVD (chemical vapour deposition).