Bomb making requires the "Bomb Preparation" skill (a silver Intelligence talent), so Geralt can not make bombs until he reaches level 15 at least (and then only if it is really a priority as other talents are much more useful). He can, however, use any he finds. Bombs require , just like potions, but the bases are different. All bomb-making bases are referred to as "black powder" irrespective of the actual colour of the item.