Few minerals on the planet exhibit such a range of useful properties and natural beauty as quartz. It may form gorgeous crystals in an array of colors like citrine, rose quartz, and amethyst, or form fine layers of agate. Its toughness makes it useful for a variety of industrial applications, while odder features like its piezoelectric properties keep watches on an accurate rhythm. It occurs all over the world, yet the variety of its habits make some pieces of quartz rare and valuable gemstones. In a way, quartz is the quintessential mineral.