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The word 'diamond' is derived from the Greek adamas, meaning

Diamond is one of two common naturally occurring crystalline
forms of the element carbon, the other being graphite.

Diamond is the hardest natural substance on Earth, while graphite
is one of the softest. The difference lies in their crystal structure and
relates to where they crystallized - diamond is the high-pressure
form whereas graphite is the low-pressure form of carbon.

On Moh's hardness scale of 1 to 10, diamond rates as 10 whereas
graphite has a hardness of about 1.

Although extremely hard, a diamond has planes of weakness within
the crystal structure that make it brittle, hence a diamond may
shatter if struck with a hammer.

Diamonds have the highest thermal conductivity (ability to
dissipate heat) of any known substance, this makes them very useful
for cutting and polishing.

The very high refractive index and power to disperse light gives
diamond the brilliance or 'fire' that is so valued. A well cut diamond
returns a greater amount of light to the observer than a gem of lesser
refractive power.

A gem-quality diamond is any clear diamond, free of most
inclusions, cracks and other flaws. Its hardness and rarity makes a
diamond unsurpassed as a precious gem.

About 45% of Argyle's production are industrial diamonds. Their
hardness makes them very useful as abrasives for cutting and

Colouration in diamonds is usually due to impurities within the
crystal lattice. Today colours such as pale blue, yellow and even
brown, are promoted as gem specialities.

Pink diamonds are the rarest of coloured diamonds. The 'Argyle
Pinks' are even more special because of their depth of colour,
ranging from delicate pastel rose to full-bodied purple.

Diamonds are measured in the old units known as carats - one carat
= 0.2 grams. Note, a carat to measure diamonds is very different to
the 'carat' used to describe gold purity.