How are gems cut to achieve a perfect finish?

We use a lot
of different gemstones in our jewellery and we also use a variety of cuts to
achieve the right look and proportions in each of our pieces. This means that our gem store is a magpie's
heaven; full of glittery, shiny materials all ready to be transformed into
stunning pieces of jewellery. You may
have wondered how gemstones appear naturally and how gem cutters (also called
lapidaries) achieve the brilliant sharp edges and smooth faces we see in our
jewellery, so here are some answers.
Most
gemstones are found naturally in a very rough state and in many cases they're
unrecognisable as gems – to the untrained eye they can look like plain old
rocks or standard crystals. It’s the processes
they undergo after being mined that transform them into what we are familiar
with. As most gemstones are found in
large lumps, the first stage of processing is to cut them into smaller
pieces. Depending on the nature of the
stone, as well as the size of the piece, it may be cut into slabs for further
processing or into even smaller pieces which may then be individually worked or
cut into more stones. Very small pieces
of expensive natural gem may be worked from their initial state into the
finished product without being split at all.
Once the
large chunk has been sawn into smaller pieces, it can then be ground into one
of many standard shapes (the shape at this stage of processing often informs
the final cut style). At this stage the
stone is known as a “rough”, and it's where we get the phrase “a diamond in the
rough” from. Diamond or silicon
carbide is used as the grinding surface, as they're much harder than any other
stone they might have to work. Water or
oil is used to lubricate the surface of the stone and prevent it from
overheating from the friction – some gemstones are heat treated to change their
colours, but no-one wants to accidentally change the colour of a stone through
processing.
If the stone
is to be left rounded, it is then sanded on a flexible surface like a belt
sander to refine the surface and keep it smooth and rounded. Cabochon cut stones are prepared in this way,
but the finer polishing and shaping is done with progressively less abrasive
materials like felt and leather. If the
stone is to have facets, that is to say flat areas on the stone which make up
the cut style, then the stone is lapped.
Lapping is similar to grinding except that it is done on a single
surface, so each facet is worked separately.
It is then finished off by being polished to a high shine, in the same
way that a cabochon cut stone is finished.
Processing
gemstones in this way requires a steady hand, a high degree of visual accuracy
and judgement, as well as the ability to envisage how a rough stone will turn
out if cut into a given shape or style.
The skill of gem cutting lies in getting the biggest and best cut stone
from each piece of rough gemstone and it is something which takes many years to
perfect. People who cut diamonds from
rough are highly skilled and trusted with the most expensive natural material a
jeweller may ever work with, so they must be very experienced. The gem cutters who work on the stones we use
in our jewellery are very experienced and skilled at getting the best stone
from each piece of rough they work with, and they must meet our high quality
standards because we want to use the best we can get for our customers.
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