Gemmies are EXTREMELY durable. Gemmies are made with intense pressure, which is very difficult to break. No matter the surroundings, Gemmies can survive through anything.
Gemmies can easily be put in your pocket. They are small enough to fit almost anywhere, but not too small to be able to loose them. They are lightweight and easy to bring around.
Gemmies are divisible. They can easily be divided in exchange for goods of varying values. For example, when one has to pay the dragon 10 Gemmies for protection, but has 15 gemmies, they can divide up their Gemmies to pay the dragon 10 Gemmies.