Transparent, coarse-grained variety of the silica mineral quartz. Citrine is a semiprecious gem that is valued for its yellow to brownish colour and its resemblance to the rarer topaz. Natural citrine is rarer than amethyst or smoky quartz, both of which are often heated to change their natural colour to that of citrine. Citrine is often marketed under various names that confuse it with topaz to inflate its price; it may be distinguished from topaz by its inferior hardness. It occurs mainly in Brazil, Uruguay, the Ural Mountains, Scotland, and North Carolina.