Of all the gem species on the planet, Quartz is the largest species with gemstones in the Crystalline, Micro-crystalline and Crypto-crystalline varieties. Quartz comes in transparent to opaque qualities in almost every color known. Examples of Quartz varieties in the Crystalline group are Citrine, Amethyst, Rose Quartz & Crystal Quartz; in the Micro-crystalline group are Jasper and Agate; and in the Cryptocrystalline group are Chalcedony. Being the most plentiful gem, Quartz is found worldwide.