Every week someone at the counter picks up a cabochon and asks, "How do you even make this?" Short answer: you saw it, mark it, trim it, grind it, sand it and polish it, and you keep it wet the whole time. The long answer is below. The photos are from my book, Beyond Cabbing: A Lapidary Handbook, so this is how I actually do it in the shop.
What a cabochon is
A cabochon, or "cab," is a stone shaped and polished instead of faceted. The simple cab has a rounded top and a flat bottom, and a double cab is rounded on both sides. The oval is the traditional shape, probably because your eye doesn't catch small asymmetries in an oval the way it does in a perfect circle.[1] Cabs are how you show off pattern and colour in opaque and translucent stones like agate, jasper, jade and rhodonite. They're also the only way to bring out a star or a cat's eye, which needs a high dome.[1]
Step 1: Slab the rough
Most rough is too big to grind straight away, so it goes through a slab saw first. That's a saw with a vise and carriage that clamps the rock and feeds it through, a lot like slicing bread off a loaf. In my book I call anything bigger than a golf ball slab material.[2]
Slabs are traditionally cut at 4 mm, which is a good thickness for most cabs. When I want room to carve, dome deeply or add relief, I go 5–6 mm.[2]
Step 2: Pick your spot and mark it
This is where the art comes in. Move a template around the slab until the pattern sits where you want it, avoid cracks, and trace the outline. An aluminum or brass scribe works well because it leaves a line that doesn't wash off on the wheels. Take your time here, because every step after this just follows the line.
Step 3: Trim away the waste
Trim saws hand-feed the stone through a stationary blade, like a little table saw, and you use them to cut the excess off around your marked cab.[2] My rule from the book: if walking to the saw, making the cut and walking back is faster than grinding, trim it. You'll save your wheels and your patience.[2] Make several straight cuts that come close to the line without crossing it.
Step 4: Dop it
Dopping means sticking the stone to a handle, usually a wooden dowel, with hard wax. Warm the stone and the dop wax, seat the stone flat side down, centre it, and let it cool completely before you grind. The dop gives your fingers distance from the wheel and lets you roll the stone evenly.
Step 5: Grind to the line, then form the dome
Grinding wheels are water-fed diamond. Think of them as fast, spinning nail files.[2] On the coarse wheel, grind the outline right to your scribed line and keep the sides straight. Then add a small bevel around the bottom edge so it doesn't chip and sits cleanly in a bezel. Finally, start shaping the dome by rocking the dop in smooth arcs and rotating as you go. Don't push hard. Let the wheel do the work. If the stone gets hot, stop and let it cool on its own. Dunking a hot stone in cold water is how you crack it.[2]
Step 6: Sand through the grits
Move up through progressively finer wheels, and at each step erase the scratches left by the one before. Scratches you leave behind now will still be there under the polish, guaranteed. Wash the stone and your hands between grits so coarse grit doesn't ride along. Once you're on the pre-polish wheels, don't set the stone on top of the machine. Vibration plus dust turns the housing into a scratchy lap.[2]
Step 7: Polish and remove
Finish on a polishing pad with a compound that suits the stone. When it reflects a window cleanly with no haze, it's done. Pop it off the dop by chilling the wax or warming it gently, then clean off the leftover wax.
Keep it wet
Every step above is done wet, for the stone and for your lungs. Quartz-family stones throw silica dust when you work them dry. I go through why in my post on silica dust and wet cutting.
Ready to try? Start with something forgiving, like a jasper or agate from our opaque lapidary rough, and grab supplies from lapidary tools. Or skip the work and browse finished cabochons.
References
- Gemological Institute of America. Gem Cutting Styles: Definitions.
- Kelliher, A. 2026. Beyond Cabbing: A Lapidary Handbook, Volume II: Appendices & References. Appendix A, Lapidary Safety, pp. 16–21; Appendix H, Sawing, pp. 90–92.
By Adam Kelliher