A Black Beauty is a coin that spent too much time in the annealing furnace. Which caused them to come out looking darker than a normal nickel clad planchet. The black on your coin happened in circulation, and not pre strike. This is easily told by the bubble seen on your coin. When this coin was subjected to a massive amount of heat, it caused a separation between the clad layers, and the bubble formed.
ED, Environmental Damage. An added explanation to a PMD, Post Mint Damaged coin. That would make a fun coin to experiment with cleaning, in my opinion.
Not a black beauty. The quarter is a sandwich coin. With an inner core of copper sandwiched by outer layers of nickel/copper. As explained the nickels can be black beauties as they are an alloy of 75% copper and 25% nickel. The planchets are annealed before being rolled out. If they cook too long, they can have a black beauty appearance. 1958 and 1959 are common years for that. Your coin is either environmentally damaged (rusty) black is one of the ED colors. Or as mentioned, heat was applied either accidentally or on purpose. Spender.
