A salt lick is sedimentation of mineral salts which are used by animals to supplement their nutrition which ensures they get sufficient minerals in their diet.
Horse rearing requires passion and knowledge about equines. The physiology of a horse’s body differs significantly from that of a human body and even though they require same nutrients as we do, the quantities are often different.
You need to stop depriving your horse or horses of one of the greatest source of minerals, i.e. Himalayan salt licks.