The Turquoise Mystic
Cutting a freeform cabochon.
by Tom & Kay Benham

Make the Mystic Bezel to go with this cabochon.

Beginner-to-Intermediate project

Have you ever admired the rough, craggy beauty of a turquoise nugget that's been ground and polished to expose its beautiful color, yet retained its natural texture? Our project will guide you along the pathway to this distinctive lapidary style.

Naturally, the first step is to locate a suitable turquoise nugget. We chose one with a bubbly surface, sometimes referred to as seafoam. Once you've chosen your nugget you should become familiar with it, study it and determine how the stone wishes to express itself. The nugget will tell you which side is the front and which is the back. Once you open your mind, the true shape of the stone will be revealed.

Most of us have been taught to force a perfectly calibrated cabochon shape from our sawn slabs. However, with this turquoise nugget, we won't force the shape. Instead, we'll let our nugget tell us where to cut and polish in order to achieve a pleasing combination of natural roughness and turquoise color. If this is beginning to sound like a mystical experience, then you're catching on. Working with turquoise is mystical — with the nugget communicating its true form to you. Working at the grinding machine, even I, an engineer by profession and a guy with both feet firmly planted on the ground by temperament, seem to lose all sense of time and become one with the stone!

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	• Genie Lapidary Grinding Machine or comparable grinding machine, with complete set of diamond wheels: 80-, 220-, 280-, 600-, 1200-, and 14000-grit and a leather polishing disc • Flat lap machine with 325-, 600-, 1200, and 3000-grit diamond laps • Water in a spray bottle • Holy Cow Polish™ polishing compound or compound of your choice
For information on supplies, please see the Annual Buyers' Directory. Always ask for the MSDS (Material Safety Data Sheet) for any materials you buy, which will give you reactivity, health hazard, and safe handling data.

 

Make the Mystic Bezel to go with this cabochon. Contributing Editors Tom & Kay Benham teach metalsmithing in the Tampa Bay area and intarsia at the William Holland School of Lapidary Arts (GA) and at Wildacres Retreat (NC) for the Southeast Federation of Mineralogical Societies. They are also co-editors of the Florida Society of Goldsmiths Newsletter and active in the Pinellas (FL) Geological Society. Their tips column, Jewelry Journal, appears monthly.

Using the 220-grit wheel on your grinding machine, shape the outside edge, removing any protuberances that fall beyond a smooth, natural shape. Do not force it into a traditional cabochon shape — let the nugget guide you.

After determining the front of the nugget, grind away any excess material on the back using the 80-grit grinding wheel.

Using a flat lap, grind the bottom of the nugget flat, working through the various grits (325, 600, 1200, and 3000) until it's ready for polishing.

Holding the turquoise nugget vertical and at a 15° angle to the 220-grit wheel, grind all around the side of the nugget to provide a surface for the bezel to grip.

Holding the back of the turquoise nugget at a 45° angle to the 220-grit wheel, grind the sharp edge of the back just enough to prevent it from chipping. This break should be no more than 1/32" wide. As a matter of personal preference — you can either dop your nugget or handhold it as we did.

In Steps 6-8, you just want to grind enough to generate the shape without grinding away all of the natural texture of the turquoise.

Hold the top of the turquoise nugget at a 30° angle to the 220-grit wheel and grind a bevel around the top of the nugget, generating the beginning of a curve on the top surface.

Hold the top of the turquoise nugget at a 45° angle to the 220-grinding wheel and grind a second concentric bevel around the upper surface to provide additional curvature to the top of the nugget.

Hold the top of the turquoise nugget at a 60° angle to the 220-grinding wheel and grind a third concentric bevel around the top to further refine the curvature of the nugget. You should now have three planes — 30°, 45° and 60° which approximate the curved top of the nugget.

On the 280-grit wheel, begin sanding the top of the nugget, moving it back and forth across the three concentric rings to blend the 3 planes into a continuous curve. Sand just enough of the front face to define the curve. Remove as little material as necessary. For this project we want to leave some of the rugged texture of the turquoise nugget.

Continue to carefully sand the top curved surface of the nugget using each successive finer grit wheel — 600, 1200, and 14000. These sanding wheels are rubber-backed so you can press the nugget into their surfaces and the wheels will conform to the curved surface. Don't advance to the next higher grit until the scratches from the previous rougher grit have been removed.

Polish the front and back surfaces of the turquoise nugget using a slurry of Holy Cow™ and water on a soft leather disc. Polishing only takes a few seconds; it actually begins when the leather disc starts to dry out and you feel the nugget begin to pull.

We are firm believers in polishing all surfaces of a stone, as this seals them, reducing the absorption of oils, sweat, and water which can cause stains and/or color alteration. An additional benefit of polishing the back is that the finding can be designed so that the back surface of the stone can also be displayed.

If you've been sparing in your grinding and polishing, your turquoise nugget should exhibit a pleasing combination of color and surface texture. Remember that each piece of turquoise is different and each requires a different approach. So listen to your stone, it will guide you through the process. Always remember the most important rule of lapidary work — grind a little and look a lot!

Next, we'll make a bezel setting for your free-form cab!