How it is formed: Citrine is of the quartz family, made up of silicon and oxygen and can be formed within all types of rocks. It is most commonly created by heat treating purple Amethyst to about 900F, and is fairly rare in nature. It is possible to find in nature though, and the rarer gems tend to be a light and transparent yellow. Natural citrine is most popularly mined in Brazil, but is also found in the United States, Argentina, and Madagascar.

Color: Yellow to brownish red variety 

Natural citrine is more yellow

When heated at higher temperatures, the stone becomes a deeper red-brown / orange

Mohs Hardness Scale: 7, citrine can be cut into almost any shape or size 

Compound: SiO2 - Silicon Dioxide