Diamond is a naturally occurring mineral with an extraordinary
crystalline structure and strong chemical atomic bonds that
account for its strength and durability. The carbon atoms that
form diamond are released when the rocks carrying them melt
under intense heat. These atoms, given an environment of the
right levels of heat and pressure, bond together and start to
form diamond crystals. It is, however, a very delicate process
since a small increase in temperature causes the crystals to
melt, and a drop in temperature halts their growth. Diamonds
were formed at least 990 million years ago, although some are
estimated to be as old as 4.25 billion years, older than life on
planet earth. They were crystallised in various types of rock,
under enormous pressures of 45–60 kilobars, at temperatures of
900–1000 centigrade, and at depths of 125–200 kilometres below
the earth’s surface. Some rare specimens developed at depths of
300–400 kilometres. Kimberlite, or diamond-bearing ‘pipes’, are
formed when magma, or molt