Black Coin

A Black Coin are coins in Super Mario Run and are seen after the player has collected all five Pink and Purple color coins in any level. Despite their name, they appear to be a dark pine green instead of black. 
Black Coins are often positioned in hard-to-reach areas, and all five must be collected in a single run in order to be marked as completed. Unlike Pink and Purple Coins, Black Coins are not attracted by a Starman. Upon the results screen at the end of the level, each Black Coin is counted as ten regular coins towards the player's high score. Rally Tickets are awarded when collecting all five Black Coins.
No further types of color coins are seen after collecting all Black Coins in a level. The Black Coins will still be seen in the same positions if the player re-enters the level, and may be collected again with no further effect. Collecting the Black Coins in all twenty four courses will cause a Black Coin Pipe to appear on the Kingdom Builder, which grants access to the level Make the Cut!.
As of the version 3.0.4 update, if players collect all Black Coins in World Star, a Gold Star Pipe will be available to place in the kingdom, which will grant players access to the level Red Block Run.