A cabochon is a gem polished to a smooth, convex dome, with no facets. It is one of the oldest and simplest cuts.
In more detail
Star and cat's-eye gems are usually cut as cabochons to show the effect best. A double cabochon is domed on both sides. The cabochon is popular for colored stones but rarely, if ever, used for diamond. Diamond's extreme hardness makes a smooth, rounded surface hard to polish.
Related terms
- Chatoyancy: Chatoyancy is a single band of light that glides across a gem, like the slit eye of a cat. Light reflects from many aligned, needle-like inclusions.
- Asterism: Asterism is a star of light that glides across the dome of a gem. Light reflects from fine needles, often rutile, that lie in two or three directions.
- Opal: Opal is a gem made of silica that water left in cracks of underground rock. Precious opal is made of tiny spheres stacked in a grid, and these diffract light into play-of-color.
- Jade: Jade is a trade name for gem rocks made mainly of jadeite or nephrite. Their tiny interlocking crystals make them exceptionally tough.
- Moonstone: Moonstone is a feldspar gem: orthoclase with thin layers of albite inside. Light scattered between the layers gives a floating glow called adularescence.