How to Cut Opals
Opals are gemstones that naturally occur in many colors and variations. Only as hard as glass, the stones can be tricky to cut and smooth without damaging them. Many find it an exciting challenge to cut and polish an opal, revealing its inner beauty.
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Things You'll Need
- Diamond saw
- Dop stick
- Heated wax
- Diamond grinding wheels (coarse to fine)
- Felt wheel
- Serium oxide glass-polishing powder
Instructions
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Cut the rough opal pieces into rubs (rough, stone-shaped pieces) using a diamond saw. Leave the rubs as large as possible while still cutting off all parts that you don't want to work with. Remove cracks, potch (colorless parts of the parcel) and excess pieces of stone. Use cool water while cutting to avoid burning or cracking the opal.
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Stabilize the opal. Use heated wax to adhere the opal to a dop stick. A dop stick is a small, thin wooden dowel or a large nail. A dop stick allows you to hold on to the opal while working with it.
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3
Slowly shape the opal. Start with a coarse diamond grinding wheel and work toward a fine wheel. Work to remove any imperfections on the stone itself as well as marks you may have created earlier when cutting the opal with the diamond saw. Most opals are fashioned into dome shapes called cabochon.
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Polish the opal with cerium oxide (a glass-polishing powder available at car parts stores) and a felt wheel doused in water. Once you have polished the opal to your satisfaction, remove it from the dop stick, turn it over and restick it to the dop stick with the back (unpolished side) of the stone facing up.
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Cut the back of the opal flat using the grinding wheel. The correct shape for the back of an opal is flat with the edges tapering up toward the center of the sides, or girdle, of the opal. The taper helps a jeweler place the opal securely into a setting.
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Tips & Warnings
Purchase parcels (bulk opals in their rough, natural state) from opal miners or dealers. Dealers may offer everything from a single stone to a bulk lot of rough rocks. Educate yourself before purchasing rough opals. According to Mike Kelley, the author of an opal-purchasing guide, many dealers rate their opals higher than they should, and even a money-back policy does not guarantee you're getting good stones.
There is more than one way to cut and polish an opal. Jack Slevkoff, a writer for GemWorld.com, offers a slightly different technique and a list of specific tool brands for opal cutting. (See Resources.)
Start with a large stone. As you cut and shape the opal, take care not to remove too much of the stone, or you may end up with a tiny piece that cannot be used.
