Cutting diamonds to make them look good
How to clean diamonds
Artificial treatments to improve the way a diamond looks
How much is a diamond worth?
Diamonds are crystalised carbon.
Graphite (the lead in pencils) is also crystalised carbon,
but a different crystal form.
Diamonds will burn (please don't try this at home!)
A diamond was believed to protect the wearer from the
Devil, as well as the Plague.
Diamonds are very hard, but like many other gemstones they
are somewhat brittle, so a violent blow can crack or chip the
stone. We see many old rings, and often the diamonds are
Note the different colours as the light is refracted in the
above stone, because the crystal breaks up light like a
prism (this colour effect is called fire). Also you can see
various fractures and inclusions, most in the top left of the
stone. Just one is clearly visible near the centre, but
good cutting means most are towards the edge. Click here for larger
Over 120 miles (200km) below the earth's surface and upto 3
billion years ago, temperatures of 1100C and the incredible
pressure of 65,000 atmospheres allowed diamonds to form.
Aeons later, rocks like Kimberlite transported these precious
stones towards the surface.
Diamonds are (as we all know) the
hardest natural substance, so can be used for cutting any material; they
were used to cut the intricate marble designs on the Taj Mahal.
first became interested in jewellery, I did not appreciate diamonds.
However admiring their beauty under the microscope, and seeing these various
inclusions and the beauty of their crystal structure has resulted in my coming
to regard them among the very best of gems.
Cutting and Shaping
This is the starting point: a diamond fresh from the ground.
The small triangles are the crystal facets. This diamond
won't be cut for jewellery, it has too many flaws and
Click here for larger image (169KB).
Their hardness makes cutting the facets, which cause the sparkle and fire,
very difficult. Faceted stones have only been around a few
hundred years. Finally in 1919 scientists worked
out how to maximise the sparkle and fire by cutting the facets at the perfect antle.
Diamonds can only be cut or polished by another diamond. This
works because diamonds are harder at some angles than others - a
result of the crystal structure. Before cutting, the craftsman
will ensure that no facets lie along this line of maximum
hardness - because these would be impossible to cut or polish.
Provided that particular angle is avoided some of the diamond
dust used for cutting and polishing will be harder than the
diamond which is being worked on.
Diamonds may look clear but actually they have varying tints from
blue white towards brown. Blue white commands the highest price.
Coloured stones do occur, and if attractive are very
valuable. Most diamonds are too flawed to be worn as
jewellery and are used in industry for cutting and grinding.
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Many fascinating inclusions are found in diamonds, including
garnet crystals. The clarity of the diamond means these
inclusions really look superb. Sadly the most common are
dull black spots, often called carbon, but more often actually
sulphide as in the picture below.
This is a rather attractive black spot, which I call
'The bee.' Luckily it's so small it doesn't
spoil this stone. Many diamonds have larger black
inclusions (and less fascinating shapes), which reduce the stone's value. Fractures are also common; if they
are small, the stone is not weakened.
In the best stones flaws are only visible through a powerful
lens, in cheap stones you will see them with the naked eye.
So the price for a blue white stone which looks clear to the
naked eye will be many times more than the price for a yellowish
stone with black spots!
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Cleaning is simple - they won't be affected by hot water.
Make sure the back of the stones is kept clean, use a proprietary
jewellery cleaner or a detergent, but not soap - diamonds attract
grease and fats, and most soap contains some fat. While you
can clean the stone for yourself, we recommend you get a jeweller
to clean and examine your diamond jewellery every year.
Replacing a diamond is expensive, so it makes sense to have your
jewellery checked to ensure the stones are secure.
Almost all diamonds are sold in their natural state. But
diamonds can be 'clarity enhanced' by filling a fracture
to conceal it. Also black spots can be removed by using a
laser to drill into them, then bleaching the mark. However
these treatments may not be permanent. Fracture filling can
deteriorate with time, and repairers have encountered problems
with laser-drilled stones. Stones can be
'colour enhanced' by coating with a substance which hides
an unacceptable colour tint. The treatment is not
You can buy with confidence in the UK, because the law requires
that you are notified before purchase of any such
treatment. As a result, few 'enhanced' diamonds are
sold; but it is wise to buy from reputable dealers.
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Price depends on many factors.
First there is the weight, larger stones are [obviously] worth
more. But quality is even more important than weight.
Inclusions can really spoil a large stone and make it look
dull. What about the cutting of the facets? If the
angles are wrong, much less light will be refracted within the
stone, and it will have less fire.
Finally consider the colour. Some stones look yellowish
when compared to good diamonds. They look disappointing,
and that will bring their value down a lot.
But the final test is your judgement. Two stones may seem
identical when described, yet one could be much more appealing
when seen, and that is the one which is worth more to you.
And that is why it's so wise to view a diamond before
buying. If you are viewing stones in different shops, take
along a diamond (perhaps in a ring) or CZ and compare the gems which interest you to
that reference stone. That will help you make allowance for
different lighting etc in the shops.
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