Black Nickel

its lustrous its it shines in the light the you can see the light reflections from the scanner specially on the nicks above his eye and the Monticello building

well maybe not technically black added a regular nickel for comparison

Unfortunately, it is impossible to judge luster from scans alone. Normally, I would think "environmental damage" and just move on but this is one of the elusive 2010 nickels so it has not been in the wild very long for it to have sustained environmental damage. A dark, but lustrous, appearance can indicate a sintered or improperly annealed planchet error. They key is that the coin must have a lustrous appearance with a cartwheel effect just like a freshly minted normal coin, environmental damage or a coating would dull the luster. The darkness can be caused by leaving the planchets in the annealing oven too long(planchets are heated before striking to soften them) or a fine coating of metal dust adhering to the planchet in the annealing oven which then bonds to the surface of the planchet. Because this happens before the coin is struck the striking of the coin imparts luster to an otherwise dark coin.

I think it could be post mint environmental damage of a chemical nature. Metals can tarnish in an oxidising environment. Oxidising agents are those chemicals that carry oxygen (obviously logical), but other oxidising agents are those chemicals that carry chlorine or sulphur. Metallic sulphides are often very dark or black in colour. Since a nickel is 75% copper, I would suspect that the coin has a very thin coating of (mainly) copper sulphide.

Found another one

Just read in a book that the dark color comes naturally from an incorrect alloy mix. Way to much copper is used and colors range from blue, purple, to black. It goes on to say that these nickels are highly collected, but says nothing about added value. Anyone know if this is true?