Amethyst
The amethyst has a purple color, or sometimes is like violet or like drops of wine or like a rose. Some there are which turn almost white, others are like red wine mixed with water. From India it comes; it is easy to work, and it prevents intoxication. It would be precious if it were not so abundant, but it is commonplace since there is so much of it. There are five kinds.
Geratite
Geratite is black. It is of such a nature that if a man opens his mouth and puts the stone under his tongue he will divine what another person thinks of him, and can win any woman's devotion. This stone can be tried as follows: let a man anoint himself with milk and honey, go out into the sunshine where insects swarm, and if he has the stone in his mouth the insects will not attack him; if he removes the stone they will at once sting him.