These rock hard salt licks contain many of the valuable minerals your horse needs to promote a healthy balance in the body. Iron, potassium, and magnesium are particularly useful in replenishing electrolytes lost during hard work. It is these minerals that give the Himalayan Rock Salt its signature rosy color. The Centaur® Himalayan Rock Sock is 100% all natural and is literally “rock hard” so it can be left outside. Machined to fit most novelty salt lick holders or comes with a rope for easy hanging without a holder.