The word "citrine" has a few potential sources, all related to citrus fruits. The most likely root of this word is from the old French word citron, meaning "yellow," or the Latin word citrus, in reference to citrus fruit. Around the 17th century, both citrine and smoky quartz were called "cairngorm" after their source in the Cairngorm Mountains of Scotland. "Madeira citrine" is the term used for warmer, reddish orange citrines, so named because they share their color with Madeira wine.
Citrine is one of the most valued and popular gemstones in the quartz group. Some Biblical scholars believe that citrine was the tenth of 12 stones in Aaron's breastplate described in the book of Exodus. The stone was referred to as chrysolitus (Greek for "golden stone") in both Roman Catholic and Latin versions of the Old Testament, leading to some confusion over whether it was citrine, topaz, or beryl. However, in the King James Version, the tenth stone is referred to as beryl, meaning it would be heliodor, and modern scholars believe the stone was actually topaz.
While many citrines on the market today are actually heated amethyst or smoky quartz, citrine does occur naturally in beautiful golden and brownish-orange hues. It's also possible that quartz crystals that grew naturally as amethyst or smoky quartz were turned into citrine by natural heat from nearby magma activity. The color of both amethyst and citrine is due to iron, determined by how the electrons are arranged.