Gems

Gems, or gemstones, are materials that have been cut and polished for use in jewelry and decorative objects. They are valued for beauty, rarity, and durability and are typically graded by color, clarity, cut, and weight. The term covers minerals, mineraloids, and some organic substances that meet these criteria.

Common mineral gems include diamond, ruby, sapphire, emerald, garnet, and quartz. Mineraloids such as opal and agate are also used as gems, as are organic gems like pearl and, in some traditions, amber. Gems may occur naturally or be produced in laboratories as synthetic or cultured stones.

Formation and properties: Gems form through geological processes or biological processes. They exhibit a range of properties, including hardness on the Mohs scale, refractive index, dispersion, and color. These traits, along with clarity and size, influence value. The traditional four Cs—color, clarity, cut, and carat weight—are commonly used to assess quality.

Treatment and care: Many gems undergo treatments, such as heating, irradiation, or oiling, to improve appearance. Some lab-grown gems imitate natural varieties. Ethical considerations and disclosure of treatments are important in the trade. Proper care varies by material, with general cleaning guidelines and avoidance of harsh chemicals recommended for delicate stones.