Cutting Process in Detail 

Many of you may have been curious about how gems are "Cut" from their natural crystals to the forms you are familiar with in jewelry. The purpose of this Webpage is to reveal what most jewelers can not explain or show you in a book. Jewelers and consumers are generally far removed from the process that typically takes place in factories at the countries where the gemstones are mined. Consider when you are reading this that I will be showing you the process from a Designer Cutter's Perspective and not the factory worker say in Thailand, Sri Lanka, China or a number of other countries where gemstones are cut. Consider, most "native" cutter's first commitment is to weight retention from the rough material, and not to creating the most beautiful gems possible. This is something Designer Cutters DO NOT DO! Their first commitment is to beauty and value!

 

The first step is always to take a good look at the gem rough and decide how to best bring out its inherent beauty, balancing factors of weight retention & faceting design and then to estimate a value if feasible. In the picture to the ring, I have in my hand a large Aquamarine crystal from Africa. Take note the irregular shape of this rough is do to the fact that even a larger crystal was broken up, literally hammered apart into this relatively "clean" piece. There are a few fractures or inclusions to work around on the left side of this crystal, so the largest gem will come from the clear area to the right.  The cutting process begins by sawing and grinding into a preform shape. If one wants to cut a suite of matching gemstones, preforms of like color, size and orientation are matched up before faceting.  When faceting, cutters are basically grinding flat surfaces on a gem material in stages.  The first stage begins by grinding on a coarse lap, a diamond impregnated wheel, to remove material quickly in order to shape the gem rough to the faceting arrangement chosen to maximize the inherent beauty of the gem.  This process is repeated 1 to 2 more times with finer grits before polishing.  The last step of polishing then utilizes a special polishing lap designed for a given gem material to obtain the highest luster. The most commonly use polishing compounds are Cerium or Alumina Oxide and 50-100 micron sized Diamond powders.

 

Left photograph shows three preforms of Aquamarine being matched up to create a suite.  You can imagine the difficulty in exactly matching the hue, tone and saturation.  You can see this example is not a good match, so I then utilized the large crystal in the above photograph, to then create a perfect match.  Right photograph shows the largest gem on the polishing lap.

 

Left photograph reveals the luster of the facet after being polished.   By reflecting light off of the surface you can determine the quality of polish and when to go on to the next facet. (Note: a "Designer" gem cutter cuts the pavilion(bottom half) of the gemstone first in order to have ideal angles to reflect as much light as possible back through the gemstone. "Native" cutters are taught to cut the crown(top half) of the gem first in a flat manner and then the pavilion in order to retain weigh.  They are told to "just finish off the bottom".  The results are optically incorrect angles that create large windows, poor symmetry, bulges that adversely affect beauty.) Right photograph shows the desired final result: a perfectly matched brilliant suite weighing a total of 64.95 carats, where the center gem is over 30 carats in size! Another example illustrated below is a very large Tsavorite Garnet, at the time one of approximately 10 this size mined in Kenya, East Africa per year.

 

This specific gem poses a challenge to the gem cutter.  Analyzing the optimum shape to cut while removing the numerous inclusions and surface characteristics to retain as much weight to produce the most valuable gem, is a time consuming process.

 

Left photographs reveals the first step of grinding the flat surface that will be the table facet of the gem (largest facet on the crown).  You can see in this photo I am grinding down to remove all surface imperfections and still need to go a little further. Right photograph reveals the other side of the gem that has a large and deep fissure I will have to overcome.

 

After I have finished grinding the table surface, I mount it to a "Dop Stick" and attach it to my faceting machine.  Left photograph shows me centering the material on the Dop to optimize removing all necessary inclusions for an optimum shape. You can see I have also ground on the sides of the crystal to create a reference side for the shape I have decided in my analysis, which is a cushion. Right photo reveals the fissure present on bottom of the material that can not remain in the finished gem and also the how I will orient the reference side with my machine.

 

Given the value of this material, I have chose to saw a slice off of the pavilion through the fissure at the correct angle instead of grinding the material away.   By doing this I have saved a small piece of the gem which can later be cut into a smaller gemstone.  Left photograph shows how I mount a saw blade on my machine and slice off the desired area. Right photograph shows the results where only a small portion of the fissure remains which is exactly what I wanted to accomplish.

 

The next step is to rough grind the main facets of the pavilion to remove most of the inclusions as possible. Left photograph still show there is still inclusions to be removed around the edges and in the center of the gem.  Right photograph illustrates the cushion outline and pavilion before polishing. Note there is no longer any inclusions visible.

 

Left photograph show the pavilion after polishing. The next step is to cut the crown by first transferring the gem to another dop stick.  Right photograph show the finished crown and the gem still mounted on the machine. The gem appears overly dark because it is still mounted to the dop stick and can not reflect light back to your eye.

 

These two photographs reveal the final result. A very rare 4.80 carat fine Tsavorite Garnet. A very good yield given the inclusions and deep fissures of original crystal and resulting finished gem was cut to have no visible inclusions in the gem.

Special thanks to Cambell Bridges, geologist and miner of Tsavorite in East Africa & Yianni Melas, gemologist and friend whose efforts obtained the fine Aquamarine from Mozambique, Africa.