Bloonstones

Bloonstones  are a type of currency in Bloons Monkey City. Their appearance is of a blue gem shard and are obtained through multiple ways, including completing a tile with no lives lost (rewards 5, or 10 in Hardcore Mode), leveling up (rewards 20), winning a Volcano Terrain tile or a cave tile, or by watching some videos (earns a varying amount of Bloonstones, not available to everyone).

They are also able to be bought via NK Coins at the Premium store. For each Ninja Kiwi coin, the player is able to purchase 5, though the more NK Coins the player decides to spend, the more bonus Bloonstones they will receive.

Uses

 * Finishing a building or an upgrade of a building (1 minute = 1, but if it last more than 30 minutes, it is a bit different)
 * Buying City Cash (Ratio: 40 City Cash = 1)
 * Purchasing and spending extra Bloontonium (Ratio: 40 Bloontonium = 1)
 * Researching (From Lead Bloons and above and for 3rd and 4th tier upgrades)
 * Starting with extra cash in a battle (10)
 * Using a Continue (20)
 * Restarting a MvM Attack (50)
 * If a building is damaged, it can be used to finish building repair
 * Filling up City Banks
 * Using a Monkey Boost to double the attack speed of all units for 10 seconds (5)
 * Buying a stack of 20 Red Hot Spikes [to place on the track] (5)
 * Buying more bloontonium while choosing attack type (40 bloontonium = 1)
 * Currently, it costs (850), plus cash, to upgrade all monkey towers, and (90) to upgrade all MvM bloons.