Citrine is the traditional birthstone for the month of November.
Citrine is yellow to brownish quartz (Formula: SiO2) (silicon dioxide) and resembles yellow topaz. The cause of the color is still under debate. At least some citrine is colored by aluminum-based and irradiation-induced color centers related to those found in smoky quartz (Lehmann, 1972; Maschmeyer et al., 1980). Some are colored by hydrous oxide. It has also been suggested that iron is the cause of color, as artificial crystals have grown in an iron-bearing solution turn out yellow. However, the dichroic behavior of the lab-grown crystals differs from that in natural citrine (Rossmann, 1994). Natural citrine is much less common than amethyst or smoky quartz, both of which can be heat treated to turn their color into that of citrine. Most citrine that is available is in fact heat-treated amethyst, although heat-treated smoky quartz comes from some locations. Accordingly, transitions to smoky quartz ("smoky citrine") exist, many citrines show smoky phantoms. Like smoky quartz, these types of citrines pale when heated above 200-500°C and turn yellow again when irradiated (Lehmann, 1970). There appear to be at least two types of yellow Al-based color centers with different thermal stability (Schmetzer, 1988). Since the yellow color centers are often more stable than the smoky color centers, some smoky quartz can be turned into citrine by careful heating (Nassau and Prescott, 1977). Natural citrine, as well as citrine produced by heating smoky quartz, is dichroic in polarized light. As with smoky quartz, citrine is often marked under names that confuse it with topaz, in order to inflate its price. It is easily distinguished from topaz by its inferior hardness.
Citrine is found in the same hexagonal-trigonal crystals as the other variants of crystalline quartz. Its hardness is 7 on the Mohs scale, with a vitreous luster.
Citrine occurs principally in localities that produce amethyst, and it is sometimes found as a zone of citrine within amethyst when it is known as ametrine. Gem-quality citrine is found on the Isle of Arran, Scotland; in the Ural Mountains of Russia; near Hyderabad, India; in Dauphine, France; in Minas Gerais, Brazil; in the Salamanca Province of Spain; and in North Carolina.
Some say that Citrine is mentioned in the Bible, but the "golden stone" in Genesis was probably Topaz. The Romans likely acquired Citrine in trade with the East. Their jewelers were among the first to regard it as a precious stone. Medieval Celts prized Citrine as a health-bringing amulet, and it was thought to ward off poison and disease. Later on, it became a popular choice to set within the pommel of a Scottish dagger. Queen Victoria favored the yellow gem, especially in Scottish-inspired settings.
Crystal lore states that Citrine is one of the only stones that doesn't retain negative energy but instead deflects it. As such, it is excellent in charms against lethargy and depression. Citrine is said to boost willpower and determination, but be careful--it can have an adverse effect on people prone to agitation or aggression. Citrine has a secondary reputation as a money-drawing stone, probably due to its gold color. Placing a piece of Citrine in a cash register drawer is supposed to ensure that the riches never stop flowing.