The 4C's of diamond appraisal

CUT. Diamonds are cut into a number of shapes;
round, marquise, oval, pear, heart and emerald.
The choice is a matter of personal preference.
When a diamond is cut to the right proportions,
it displays brilliance and fire. The standard
'brilliant' (round) cut demonstrates these
qualities best.

When a diamond is well cut, light is reflected from one facet to another and then
dispersed through the top of the stone. If it is cut too deep, some light escapes
through the opposite side of the pavilion. If cut too shallow, light escapes
through the pavilion before it can be reflected.

COLOUR. Diamonds come in different colours.
The 'fancies' - blue, green, pink and yellow
etc. are very rare and expensive. Colourless
diamonds are most precious, as they allow
white light to pass through easily to be
dispersed as rainbows of colour.

CLARITY. To determine a diamond's clarity, it is
viewed under 10 power magnification (10X lens)
by a trained eye. Diamond, being a natural stone,
often contains small mineral inclusions. The
fewer and smaller the inclusions, the better is
the passage of light through it.

CARAT. The weight of diamonds is measured in carats. One carat is divided into 100
'points'. One carat equals 0.2 gram. Size is the most obvious factor in determining
the value of a diamond, but two diamonds of equal size can have very unequal values,
depending on their quality.