Amethyst

 Amethyst wholesales to the trade today for a 1 cwt stone from a cost of approx. $4 for a very low grade stone to approx. $50 for an extra fine example. The price goes up to approx. $60 per cwt. for extra fine larger examples. The retail price will be several times that, depending on the retailers markup. 

Amethyst, a form of quartz, is the birth stone for those born in February. Amethyst is 7 on the mohs scale.
Amethyst is said to protect it's owner from drunkenness ( must confess...never worked for me! :-) The name comes from the Greek for Not Intoxicated.
In Greek legend, the wine god Bacchus, angry over an insult and determined to avenge himself, decreed the first person he should meet would be devoured by his tigers. This happened to be a beautiful maiden named Amethyst on her way to worship at the shrine of Diana. As the tigers attacked, she sought the protection of the gods and was saved by being turned into a clear, white crystal. Bacchus, regretting his cruelty, poured the juice of his grapes over the stone as an offering; giving the gem its lovely purple hue.
In reality, the purple color comes from natural earth irradiation and some iron impurities. It is a symbol of faithful love, and at some times in history was valued so much it was worth more than diamonds.