The "Black" you refer to on nickels is because of the nickel in the mix. A lot less is used one ant two, JFK's are clads not solid planchet and the finishing is different in production. What is thought to be cause of tHe "Black Beauty" nickel is too much cobalt in the nickel ore and how it was annealed. Clads are not annealed the same way., are plated in stock plate.