Gemology Concepts PDF

Introduction KEY CONCEPTS Most gems are minerals. To be a gem, a mineral must be beautiful, durable, and rare. Many colored stones are mined by independent miners using small-scale mining methods. An appealing name can make a gem much easier to sell. Treatments improve the marketability and availabi...

Introduction KEY CONCEPTS Most gems are minerals. To be a gem, a mineral must be beautiful, durable, and rare. Many colored stones are mined by independent miners using small-scale mining methods. An appealing name can make a gem much easier to sell. Treatments improve the marketability and availability of many gems. In spite of treatment that’s sometimes extensive, emerald is the number one colored stone by value imported into the US. Most consumers accept gem treatments if they’re ethically disclosed and explained in a positive way. Changes that take place in a gem’s source country can drastically affect its availability and price. Key Terms Amorphous—Lacking a regular crystal structure. Group—A family of gems from several closely related mineral species. Atom—The basic structural unit of all matter. Inorganic—Composed of, or arising from, non-living matter. Chemical composition—Kinds and relative quantities of atoms that make up a material. Chemical element—A substance that consists of atoms of only one kind. Crystal structure—Regular, repeating internal arrangement of atoms in a material. Disclosure—Clearly and accurately informing customers about the nature of the goods they buy. Mineral—A natural, inorganic substance with a characteristic chemical composition and usually characteristic structure. Natural gems—Gems produced by natural processes, without human help. Organic—Produced by, or derived from, a living organism. Phenomenon—An unusual optical effect displayed by a gem. Facet—A flat, polished surface on a finished gem. Rock—A natural material composed of masses of mineral crystals of one or more kinds. Gem species—A broad gem category based on chemical composition and crystal structure. Silicate—A mineral that contains the elements silicon and oxygen. Gem variety—A subcategory of species, based on color, transparency, or phenomenon. Source—A gem-producing country or area, or a particular mine in that area. 35