Many people are magic users that can do various magic.But they often do really tiny ones,such as levitating a coin,ir lighting a candle.He can do better ones but only with catalysts.Basically his mom was an alchemist and a sorceress,but unlike with pure witches,she learnt most if it.Therefore only a smll fragment is in Gerald.That's why he needs catalysts,like the tiny gem,or teeth of creatures.