Intro to Stone Cutting: Beginning the Lapidary Journey with Freeform Cabochons

Lapidary work has long been on my bucket list; I’ve been collecting and cracking open rocks since I was a little girl. The idea of being able to purposefully and cleanly slice into one, to see something inside that no one has ever seen before, is so exciting to me–and besides the unseen, the thought that I might uncover something spectacular in it, maybe some geode crystals or a gorgeous pattern, makes me almost giddy.

Alas, I have yet to set up lapidary tools and a work station so I can practice stone cutting, but I do intend to take a lapidary class soon. Meanwhile, I get ready by reading and studying the stone-cutting patterns and projects in Lapidary Journal Jewelry Artist magazine, like this beginner- to intermediate-level project from contributing editors Tom and Kay Benham.

The Turquoise Mystic: Cutting a Freeform Cabochon
By Tom & Kay Benham

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!

Tools and Materials:

turquoise nugget
Genie Lapidary Grinding Machine or comparable grinding machine
complete set of diamond wheels: 80-, 220-, 280-, 600-, 1200-, and 14000-grit
leather polishing disc
flat lap machine
325-, 600-, 1200, and 3000-grit diamond laps
spray bottle of water
Holy Cow Polish polishing compound or compound of your choice


1. 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.
2. After determining the front of the nugget, grind away any excess material on the back using the 80-grit grinding wheel.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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.
8. 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.
9. 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 three 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.
10. 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.
11. Polish the front and back surfaces of the turquoise nugget using a slurry of Holy Cow Polish 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!

Keep going by making Tom & Kay’s reticulated silver bezel for this or any other cabochon.

Lapidary Journal Jewelry Artist magazine is the ideal source for more stone-cutting and jewelry projects by Tom and Kay Benham, as well as projects and patterns for faceted and cabochon stone cutting projects from other lapidary experts. Now you can receive all that expert info and keep a tidy desk by getting an entire year (all twelve issues of 2009!) of LJJA on a convenient collection CD!





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