The Gem of the Frail Scholar is an essence gem. It gives a slight Mind bonus and boosts the experience points received from reading books, but lowers the player's Body score. It can be found in the Pirate Lair — specifically, in the area opened by the explosion after players lower the Marvelous Dragonfly.
In-game description: "This gem makes everytime you read a document give you 100%+ the experience you would usually have. A way you can use it without the consequences is to equip it only for reading, and re-equip a less damaging gem later."