Citrine is a rare, transparent, pale yellow to brownish orange variety of quartz. A trace of iron in citrine’s structure is responsible for its yellow to orange color. Since natural citrine is rare, most of the citrine on the market is the result of heat treatment, which causes some amethyst to change color from undesirable pale violet to an attractive yellow. The amethyst’s original hue can determine the richness of the resulting citrine’s yellow color. Citrine is recognized as one of the most popular and frequently purchased yellow gemstones. The finest citrine color is a saturated yellow to reddish orange free of brownish tints. Citrine has a hardness of 7 on Mohs scale. Along with topaz, citrine is a birthstone for November. It’s also recognized as the gem that celebrates the 13th wedding anniversary.