Gem Cutting Facts
Whenever I tell
someone I am a faceter,Gem cutter, I am asked about the hammers and
chisels used in the process. This false idea is no doubt the result of
the cleaving process often shown on TV. This process is used rarely on
diamonds and a few other stones. For this process to work The desired
cut must be on a cleavage plane. There are only four in diamond and
these are rarely where the best cut would be. The only reason it is
shown is because it is dramatic. Therefore most stones are split by
sawing.
The rest of the cutting
process is abrasive. The picture below shows a
sapphire on a dop stick being positioned by the faceting head on a
diamond lap. This wheel is metal with diamond powder plated to the
surface with nickel. This kind of wheel must be run wet,note drip tank.
The next picture shows a 45 degree adapter used to position the table or top facet. The wheel shown here is a zinc alloy used to polish sapphire. The outer part is coated with a mixture of 3,000 mesh diamond powder and oil. The inner part is coated the same but the diamond powder is 60,000 mesh dupont synthetic diamond. The synthetic costs three times as much as natural but has the advantage of very uniform size. These particles are about the size of light itself and will smooth the facet to a final polish.
The faceting head shown below can be adjusted to any of the
teeth on the index gear. The aluminum knob at left is used for finer
adjustments. This with the angle stop determine the
exact position of a facet on the stone.
There are gears with various numbers of teeth for different cuts. Shown here are 64 80 and 96.
