Question about protection crystals

Hello friends. I have a querry. I recently learnt about protection crystals and was getting some of them , amethyst, black tourmaliine. But then i saw another witch saying that crystals can not only mess up the negative spells done against someone but also the positive spells including protective spells , basically any type of magic irrespective of their intent...i have some amulets ( and these cannot be replaced so i dont want to take risks with them) and some protective sigils and was wondering if getting the crystals will mess up all my good spellwork and my amulets and if there is any way to prevent that.