Amethyst is a violet or purple variety of quartz often used as an ornament. The name comes from the Greek a ("not") and methuskein ("to intoxicate"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication. Because it has a hardness of 7 on the Mohs scale, amethyst is treasured for its use in jewelry. However, it is still just 1/15 as hard as diamond. Due to its popularity as a gemstone, several descriptive terms have been coined in the gem trade to describe the varying colors of amethyst. "Rose de France" is usually a pale pinkish lavender or lilac shade (usually the least-sought color). The most prized color is an intense violet with red flashes and is called "Siberian," although gems of this color may occur from several locations other than Siberia, notably Uruguay and Zambia. On exposure to heat, amethyst generally becomes yellow, and much of the citrine or yellow quartz of jewelry is said to be merely "burnt amethyst." Certain gems that have shown alternate bands of amethyst purple with citrine orange have been given the name ametrine.