A cabochon (pronounced kab-e-shawn and often shortened to cab) is described as a gemstone that is not faceted, but is cut into a convex and usually highly polished shape. In general gemstones that are transparent (light passes through) are faceted, gemstones that are translucent (some light passes through) or opaque (no light passes through) are usually cut into cabochons. Also softer stones are usually cut into cabochons, as they scratch easier.
The word "cabochon" comes from the French word caboche meaning nail, and cabochons are named that because of their rounded shape. Most cabochons are rounded or domed on the top, but some may be level of flat. Some semi precious gemstone materials must be cut a specific way, such as chatoyant Tigereye, or star Rubies to bring out their special effects. Fire Agates cabochons usually have a contoured surface to best bring out the rainbow fire without cutting through it.