Precious metals and gems – usually massive, microcrystalline stones and organics – can be worked by polishing, carving, or engraving. Polishing is the oldest form of fashioning. Carving produces three-dimensional objects by cutting them from a larger mass of material. Engraved gems are made by scratching outlines or holes, or by cutting away to leave a raised image. Carving and engraving require tools harder than the material being worked.
The shine given to the surface of a stone – either by rubbing it with grit or powder or against another stone – is its polish. Dark-colored gemstones and those that are translucent or opaque, for instance, opal and turquoise, are often polished rather than faceted, as are organic gems.
They may be polished as beads or as flat pieces to be used in inlay work, or cut en cabochon with a smooth, rounded surface and usually a highly polished domed top and flat base.
Gem fragments of similar hardness may be turned into attractive pebbles by tumbling in a drum containing abrasive grits and polishing powders.
A motor-driven tumbling drum is used for polishing. The drum contains abrasive grits and polishing powder.
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