Citrine is one of the most popular gemstones available today. It belongs to the very large family of quartz (SiO2) gemstones. More specifically, it is the yellow to golden orange variety of gemstone-quality macrocrystalline quartz (silicon dioxide). The name 'citrine' was derived from 'citron', a French word meaning 'lemon', although its color tends to be more golden rather than lemon-yellow.
Natural citrine is actually quite rare and because it is more valuable than most other varieties of quartz, much of the citrine today is actually heat-treated to obtain its attractive golden color. Almost all heated citrine will exhibit reddish tints. When quartz is heated (naturally or artificially), iron impurities are reduced, resulting in lesser amounts of violet and purple, and stronger yellow to golden orange colors. The only difference between citrine and amethyst is the oxidation level of iron ions (Fe3) present in otherwise colorless quartz crystal, which explaines citrine's close relation to violet-purple amethyst, another variety of transparent macrocrystalline quartz.