A gemstone, also called a precious stone, is a mineral that is valuable, rare and often beautiful. Rubies, sapphires, emeralds, amethysts, often treasured as birthstones. Gemstones are priced and graded by carat weight. A few organic materials, like amber, coral and pearls are also considered gemstones.
are any precious or semi-precious stones, whether as mined, or cut and polished; for example, diamond, opal, etc.