gemstone

A gemstone is a mineral crystal, an organic material, or a rock that, when cut and polished, is used in jewelry or decorative items because of its beauty, rarity, and durability. In common usage, gemstones include diamonds, rubies, sapphires, and emeralds, as well as many other minerals and organic substances. Distinctions are made between natural gemstones and lab-grown or synthetic varieties that have the same chemical composition and crystal structure.

Gemstones are evaluated by properties such as hardness, color, clarity, and cut. The four Cs—carat weight, color, clarity, and cut—are widely used in grading gemstones for jewelry. Other important traits include refractive index, luster, dispersion (fire), and durability, which affects how well a gem withstands wear. Many gemstones occur as crystals in nature, formed by geological processes in rocks, or, in the case of organic gems like pearls and amber, originate from living matter.

Classification generally divides gemstones into mineral gems, organic gems, and synthetic gems. Common mineral gemstones include diamond, corundum (ruby and sapphire), chrysoberyl, beryl (emerald and aquamarine), garnet, and quartz (amethyst, citrine). Opal is a mineraloid that is also valued as a gem. Treatments such as heating, irradiation, or surface enhancement are common in the market and can affect value. Ethical sourcing and certification programs help verify origin and authenticity.