GEMSTONES and CRYSTALS are pieces of minerals that divide into precious and semi-precious stones. Broadly speaking, diamond, ruby, sapphire and emerald are considered 'precious' while all others are semi-precious. Gemologists identify stones by their chemical composition, their crystal structure and their habit which refers to the location where the stone is usually found. Gemstones are also classified into groups, types and varieties. Further classifications include light properties, hardness, fracture, colour and lustre. Material or flaws within a stone are called inclusions. Different cultures have developed traditions of crystal healing. Healers believe in the esoteric powers of gemstones. They select stones by colour and their metaphysical qualities. Wearing a gemstone as an amulet may be beneficial to physical and mental well being. This Guide presents 72 gemstones and includes physical and esoteric characteristics. Each Guide consists of eight A4 pages that fold into each other. The Guides are quality printed in full colour and protection coated on both sides. The material is a sturdy board.