Gemstones are generally minerals that have been, or may be fashioned to use for personal adornment. As a rule, they are beautiful, rare and durable. Minerals are inorganic materials with a fixed chemical composition and regular internal structure. A few gems, like amber and pearl, come from plants or animals and are known as organics. Others, called synthetics, do have a natural origin, but are made in laboratories. They have very similar physical properties to natural gems and may be cut to imitate the real thing. Almost all cut gems begin life in a crystalline embedded in a host rock known as the matrix. In this state, the stone is referred to as rough. Many natural crystals are attractive enough to be displayed as they are and others are faceted and polished to enhance their beauty, then set in a piece of jewellery or ornament. Some gem minerals such as quartz and garnets are found worldwide and others like diamonds and emeralds are rarer due to the more unusual geological condition necessary for their formation. Even when a mineral is found worldwide, only a minute proportion may be of gem quality.