Silicon and Iron

• The molecular formula for silicon.Jupiterimages/Photos.com/Getty Images
  
  Quartz is part of a classification of minerals known as the Silicon Group. The stone is made from silicon dioxide or silica. There are only eight other known substances that have the same chemical composition as quartz, but no others are as common close to the surface of the Earth. Lime quartz gets its color from being irradiated or heated after iron sulfide contaminates the mineral.
  
  

Natural and Artificial

• A chalcedony stone ring.Hemera Technologies/PhotoObjects.net/Getty Images
  
  Green quartz (or green amethyst) occurs in nature in a very dark green. Aventine is one type of naturally occurring green quartz. Other naturally green quartz minerals include varieties of chalcedony. When the process takes place in a lab the green is a much lighter, lime green. A real, natural clear quartz gemstone is used in the process but the amount of light, heat and radiation used to color it are tightly controlled.
  
  

Locations

• Lime quartz, or clear quartz that can be artificially created, can be found all over the world. Whether or not it is of adequate quality to make ornaments or gemstones is another question. Brazil presently houses a significant amount of the world's quartz mines and produces the largest crystals, but the stone is also mined and traded in the United States, Europe, Canada and Africa.
  
  

Uses

• Green quartz is one of the more unique varieties if this colorful stone, especially lime, and is often given as a gift. This fresh color makes nice accessories for a spring or summer wardrobe. It is not an official birthstone, but as it is a variety of quartz it can be used as an alternative birthstone. Lime quartz can also be a substitute for the sixth wedding anniversary gemstone (amethyst).