Yellow or gold quartz gets it's color from small amounts of iron in the crystal, and is rather rare. Commercial citrene is created by heat-treating amethyst. It is called the "Success Stone," thought to attract an abundance of power, self-confidence, and self-discipline. It is also known as the "Happy Stone". The ancient crystal healers used gold and yellow quartz to stimulate the body's healing energies, especially digestive system disorders. Citrene is the French word for lemon. Dark citrene (Masdeira Citrene) is the most valuable. Citrene turns brown when exposed to x-ray and white when exposed to heat. It is the birthstone for November and the stone for the 17th wedding anniversary.