Topaz is a common gemstone that has been used for centuries in jewelry. Topaz may be colorless, yellow, orange, red, blue and green. Its golden brown to yellow color is classic but is confused with the less valuable citrine, which is sometimes wrongly sold under the name topaz. The blue topaz that is often confused with aquamarine is rarely natural and is produced by irradiating and then heating clear crystals. Topaz is the hardest silicate mineral and one of the hardest minerals in nature. Topaz is the November Birthstone and the Sagittarius Zodiac stone. Topaz crystals can reach incredible size of several hundred pounds. Topaz can make very attractive mineral specimens due to their high luster, nice colors and well formed and multifaceted crystals.