Citrine

Citrine is the transparent yellow variety of quartz, the silicon dioxide mineral, and its name comes, by way of French, from the Latin for the citron tree. Natural stones are pale yellow, sometimes tinged orange, green or smoky, and mineralogists still disagree over which trace element colours them. True citrine is scarce in nature: both Wikipedia and Hall note that much of what is sold under the name is amethyst that has been heated, which turns a deeper yellow, orange or brown. Most of it comes from Brazil. It has been in use since the days of ancient Egypt, was long confused with topaz before modern mineralogy, and earned the nicknames money stone and merchant's stone from a belief that it brought prosperity. Cunningham assigns it to the Sun and to fire, and says it is worn at night to drive off fear and nightmares and to give sound sleep, and also to sharpen psychic awareness; he lists topaz as a substitute for it. Hall calls it a stone of abundance linked with wealth, success and joy, and associates it with cleansing, protection, grounding negative energy, intuition, creativity and self-confidence. She also notes that its colour fades in sunlight.