AZGem Gems
October, 2002

The World's Most Useful
Gem & Jewelry Monthly Newsletter

Written by Carolyn Doyle for customers of
The Dorado Company
and other visitors to the azgem.com website who subscribe.

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Usable Gems... and a little opinion.

 

Gem Faceting

Gem faceting, or gem cutting, is the process of turning a piece of mineral crystal into a gem stone.

This month we're taking a quick look into the craft of faceting a gem. In some ways the craft is very simple, and in others it is highly complex. 

In the gem world an uncut piece of material is known as rough.

Before faceting the piece of rough looks like a shard of colorful rock... or in some cases a water worn pebble.

After faceting it's a gem.

As with most other crafts, it takes a lot of knowledge and experience to do it well.

People have been practicing the craft and adding to the knowledge base for several centuries. But the advances of the past thirty years have been extraordinary. 

Advances in...

our understanding of what causes colors
knowledge of the properties of light
the crystal-related sciences
process computer uses
machine accuracy

have all contributed to advances in gem cutting.

Advances in our knowledge of the properties of light, and how it behaves in various media (air, water, minerals) has led to refinements in the angles at which facets are cut.

Different gem materials refract (bend) light at differing degrees. The facets need to be cut at a certain set of angles for amethyst... and at a different set of angles for sapphire to get bright, colorful gems.

Computers are now used to calculate facet angles for the various gem materials.

Crystal structure is somewhat like interlocking rows of bricks. For a faceter this means a piece of gem material is possibly stronger in one direction than another.

It also means the rough often shows different colors on different parts of the crystal.

So the durability and or color of a gem may be determined by how the cutter orients the piece of rough.

Modern cutting machines are more accurate. The machines are now manufactured using computer controlled equipment and more advanced materials. You can think of them as precision milling machines for gems. 

Computers are also used to control some high production gem cutting machines.

Today faceting is practiced in many ways around the world... from holding a piece of rough between the fingers and rubbing it on a hard surface, to foot pedal machines, to modern faceting machines, to high volume cutting factories.

I'm going to give you a general description of how a custom cutter we use facets a gem.

The image at right is of a modern faceting machine used by many custom cutters and hobbyists.

It has...

A flat rotating table that holds an abrasive disk
an electric motor underneath to turn the table
An arm and mast to hold the gem against the disk
a bottle to drip cooling water on the disk
Positioning controls on the arm and mast to allow the operator to cut several facets and then repeat the positioning exactly to finish polish each facet

Various grits of abrasives are used on the disks to do fast cutting and then very, very smooth polishing

Before faceting begins the piece of rough is properly oriented to produce the best color when viewed face up.

The rough is then shaped by hand into approximately the size and shape desired for the finished gem, usually using a grinding wheel.

The resulting chubby, frosty looking bit of stone with one sizeable flat spot is called a preform.

The preform is stuck on a dop stick which later inserts into the arm of the machine.

The dop stick serves as a handle to hold the preform. The preform  is stuck to the dop stick by melting a special blend of shellac and clay. For some reason this specialized material is called dopping wax.

This material is relatively easy to work with and it holds the stone securely after the wax cools. The stone is quickly released by reheating the stone and wax.

Some gem materials are heat sensitive and another method must be used to fix those preforms to the dop.

The faceter must know which gems are heat sensitive. For those an adhesive such as super glue or epoxy must be used. These adhesives take more work and clean up time.

The dop is stuck to the flat spot of the preform.

After mounting the preform in the machine the pavilion (lower) facets are coarse cut. 

After cutting all the lower facets the cutter goes back to each facet  and polishes it to a mirror finish. Great care is taken to assure that all facets meet correctly, corner to corner.

Next the cutter must work on the crown (top) of the gem.

To do this the dop stick must be removed and another one fixed to the finished pavilion. The new stick must be positioned exactly to keep everything square and symmetrical.

A special device called a transfer (or dopping) block is used to accomplish this critical task.

With the top portion exposed the crown facets are cut and polished. That sizable flat spot on the preform has become the table facet and the preform has become a beautiful gem.

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Jewelry Dealers

The jewelry dealer's program is quite a success.

New people are joining every day or two. More than a few have expressed amazement at the amount of information and practical guidance in the New Jewelry Dealer's Resource information each new dealer receives.

Now is a great time to join the program and jump start your new jewelry business. The holidays are coming soon!

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Gem Special Offers

Check out the new traffic building feature we're experimenting with. You can buy featured gems at or below our cost.

All you dealers... these featured gems are a great buy. You can increase your profits even more with these gems.

Carolyn Doyle

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The Dorado Company
P.O. Box 8232
Scottsdale, AZ 85252-8232