A cabochon stone, also known as a cabochon or simply "cab," is a gemstone that has been polished into a smooth, rounded, and convex shape without any facets. Unlike faceted stones, cabochons have a smooth and polished surface, showcasing the stone's natural colors, patterns, and inclusions.

The term "cabochon" is derived from the French word "caboche," which means a small, round-headed nail or knob. The shape of a cabochon is often likened to a rounded dome or a gently curved shape, although they can come in various profiles, including oval, round, teardrop, and more.

Cabochons are commonly cut from gem materials that have interesting colors, patterns, or chatoyancy (cat's-eye effect) that are better displayed without facets. Some popular gemstones used for cabochons include opals, turquoise, moonstone, labradorite, onyx, and many others.

The appeal of cabochons lies in their smooth, tactile surface and the ability to highlight the unique features of the gemstone. They are widely used in jewelry, especially in rings, pendants, earrings, and bracelets. Some cabochon settings may feature elaborate designs or metalwork to complement and enhance the stone's beauty.