Citrine
Citrine is the name given to yellow and orange quartz crystals. The shades can very from pale to very deep and bright.
Because these colours are somewhat rare in nature, many of the citrine crystals on the market are coloured by heat treatment.
In nature, citrine crystals may begin as amethyst and have their colour altered by heat from the earth's magma.
Citrine is the traditional birthstone for November, and is sometimes confused with similarly coloured topaz, an entirely different and more expensive gemstone.