Amethyst
This gem," says Camillus Leonardus, " is reckoned among the purple and transparent stones, mixed with a violet colour, emitting rosy sparkles." The Indian variety is the most precious. When made into drinking cups or bound on the navel, it prevented drunkenness. It is also held to sharpen the wit, turn away evil thoughts, and give a knowledge of the future in dreams. Drunk in a potion, it was thought to expel poison and render the barren fruitful. It was frequently engraved with the head of Bacchus, and was a favourite with the Roman ladies.