Platinum Shard

The Platinum Shard is a loot item that has a 7% drop chance from any bloon stronger than a Purple Bloon. By itself, it's useless, but get 1 kilogram of the stuff and you can define how much a kilogram weighs you can use it as a catalyst for random crafting, increasing your likeliness of getting something you want.

Trivia

 * Platinum is a nonreactive, or "noble", if you are a chemist, metal, so it makes a really good catalyst.