Gem Cutter, G.D.

November 3, 2010

The Optical Ride in Gem Cutting


Unlike diamonds, colored gems possess a variable of optical properties and are not cut to a uniform ideal. A well-cut colored gem exhibits an even color, an acceptable number of inclusions, a good brilliance; and it shows the majority of carat weight when viewed from the top.

Broadly, the styles of gem cutting can be divided into faceted gems (those with geometrically shaped flat polished faces) and non-faceted gems (those that do not have geometrically shaped flat polished faces such as cabochons). Now onto the four steps which I like to call ‘S.P.S.P.’ Don’t worry, this isn’t as dangerous as it sounds. (the boring intro is over folks.)

Slicing: slicing, in my opinion is the most pivitol stage when it comes to gem cutting. Why? I’m glad you asked. It pretty much determines the size and beauty of the piece of gem you’re about to cut. Once you’ve selected a piece of rough, and may I add that  you’re about to play doctor with this piece of rough.

Anyway, using a diamond-tipped circular steel saw, I, Dr. Gem Cutter, will determine how to cut, where to cut, and how many pieces to cut, in order to produce the highest quality from the rough gem. If the rough is cut incorrectly, and you’ll start to realize this when you start opening up windows in your gem stone, but that step is further down the line, its beauty may be ruined, bringing the value down  of that exceptional gem to that junk known as commercial gem stones.

Pre-forming: Once you’ve played doctor with the gem by slicing it, you can now play plastic surgeon to the ‘gems’ and start to pre-form the gem. pre-forming is typically performed by using a vertical steel grinding wheel.

The pre-forming process carries a great deal of stress. Why? I’m glad you asked. The pre-forming process determine the shape and adaptation for each gem that wants to look pretty and land itself a nice owner. So, if you screw up, mistakes at this stage can be catastrophic and every other synonym for ‘catastrophic’. When pre-forming, keep in mind the weight of the finished gem. Pretty much the weight of the gem adds more ‘bang for your buck.’ There’s always an exception to that rule if you look at cuts, color, clarity, etc… lets save that for another blog. Back to my example: A 5.23 carat Ceylon Sapphire, oval shape is at $550.00 per carat. You multiply the 5.23cts by 550pct and you get $2,876.50. Hence, ‘bang for your buck.’

Shaping: Once you’ve pre-formed the stone, its time to start shaping it and to start adding facets. In order to complete the next phase, a special type of heat activated resin or wax is used to glue the stone onto a metal rod, commonly called a dop stick.

You then grab your stone and apply it to the wax and slowly press the stone into the resin. Put the dopping stick in an upright position and let it sit till its still as a rock.  The fun is about to begin. You delicately apply the gemstone to the shaping wheel to obtain a more accurate presentation of the facets and size. Due to the immense precision required by this process, the shaper is usually a very experienced pre-former.

Polishing: The final step is known as polishing. What I like to call it is ‘opening a window.’ So your gemstones reaches  its ideal size and shape, you apply it to a horizontal polishing wheel or a metal disc that spins at very high speeds and is implanted with tiny particles of diamond. The stone is brought into contact with the disc, and a facet is born. This disc is called a “lap.” the gem cutter completes the faceting by polishing the pavillion (the bottom of the stone) and the crown (top of the stone). When you are done with all that good stuff, slightly apply the stone sitting in the wax on the dopping stick to heat. The resin will start to loosen up and with a small blade, start to peel off the wax as much as you can without putting too much force into it. Treat it like you would treat a bum of a baby. What I like to do next is drop the stone in some denatured alcohol and wipe off any last particle of unwanted wax. The best part about all this is when you reach the climax of the ‘money shot'(I.E. your finsihed gem stone) and you look at the piece of art you’ve just created.

With a few months of training and will power, you could be, potentially facetting 20 to 30 gems per day. But it may take many years to become a skilled preformer. Till next time…

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4 Responses to “Gem Cutter, G.D.”

  1. Mike H said

    Very good info…thanks!

  2. […] come to me to solve their gem cutting and inlay lapidary needs. Hell, I even blogged about it here (click the link to view the ‘gem doctor’ blog). I have a quick blog for you guys […]

  3. […] the 16x12mm size I need. If you don’t know what a dopping stick is, click this link ‘here‘, which should take you to one of my first blogs explaining the steps into the gem cutting […]

  4. […] blogs by clicking on the link to get the terminology, I.E. ‘doping stick’ by clicking here.) for a more controlled and measured feel to the shape I was aiming […]

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