The term "Black Beauty" is a nickname given by coin collectors to Copper-Nickel coins that have developed a dark, glossy, jet-black, or deep charcoal patina. This is not a separate error minting or a different metal alloy. It occurs due to an experimental annealing process or specific chemical reaction/oxidation at the mint or over time under unique storage conditions. The coin retains its sharp design details beneath the striking black finish
The "Black Beauty" Mahatma Basaveshwar ₹5 coin is a famous numismatic variation of the 2006 commemorative issue. It is highly popular among collectors due to its distinctive chemical toning and physical specifications.
