Faceting an amethyst sphere

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Here's a step by step description of how I faceted a 7 mm amethyst sphere for Cynthia's cat-and-ball ring, which was inspired by one of Tradeshop's designs.
First, I selected an appropriate piece of medium-dark purple Zambian amethyst rough.

Next, holding the stone by hand, I ground a roughly spherical preform on my cabbing machine.

I then clean the preform with a little alcohol, apply a thin layer of shellac to improve adhesion, and heat it over an alcohol flame until it's warm enough to soften a small piece of wax placed on the surface. Notice my "high tech" range -- an old juice can! Careful attention is required to avoid overheating the stone and also the potential fire hazard.

Wax is melted onto the end of a metal dop stick and the stone centered firmly in place.

The dop stick is then fixed into the handpiece of the faceting machine (in my case, a Raytech-Shaw faceter). Using an aluminum lap hand-charged with 220 grit diamond, I grind the stone slightly larger than needed and cut the larger facets. Water drips onto the lap to wash away cutting debris and prevent the stone from overheating due to friction.

Next, a copper (actually phosphor-bronze) lap charged with 1200 grit diamond and rinsed with water is used to recut all facets. This brings the stone to the desired size and produces a fine-grained surface. All traces of the previous cutting must be removed before proceeding to the polish.

Each facet is then polished on a tin lap using a thin slurry of aluminum oxide (corundum) applied with a small brush.

One side of the stone finished, I then wipe it clean with a little alcohol, apply a thin layer of shellac, and use a transfer jig to affix a new dop stick to the finished side. Then, I carefully heat the first dop stick with an alcohol flame, melting the wax on that side just enough to remove the dop. The remaining wax on that side is removed with a hot knife and then a little alcohol wipe.

The dop is reinserted in the faceting handpiece and carefully aligned, and the same steps (rough cut, fine cut, polish) are performed on the other side of the stone. A gentle heating with the alcohol lamp then melts the wax sufficiently to remove it from the dop. The remaining wax that adheres to the stone is removed with a hot knife, and the stone is wiped with a little alcohol to remove the remaining traces of wax and shellac.
The stone is then passed on to the goldsmiths at Tradeshop for their expert setting. And here's the wonderful result!

If you are interested in having some custom faceting done, please take a look at my custom work page and then check my contact page.

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