Yes. When coins are in the ground, the metal reacts to water, soil, gases, pollutants, etc. and often turns black. If the rim is the same color as the coin then it is environmentally damaged. Or toned, or rusted. Black beauties which have been improperly annealed will have a light rim (I think from the rim upset part of the minting process.) I have recovered over 2400 nickels the last 3 1/2 years and I have many of these black nickels that I dug out of the ground.