FishVille Gemstone Pouch: Everything you need to know *spoiler*
Everyone has a Gemstone Pouch, which you can access by clicking the little gem icon on the left side of your screen. This will pop open the game, and show you how many gemstones you have and how many you need to get each level of item. Collecting the required amount of gemstones will unlock the next reward for you and you will be able to purchase it. Gems work just like currency, you will have to trade them in for items and the purchase amount will be deducted from your gem balance. You can always click the "comparison" button to see how many total gems you have collected compared to your friends (if you want to brag).
To collect gemstones, you can either request them from friends or you can purchase them from the Store at a price of 5 Sand Dollars for five gems. Every one can send all four of the gems, and it doesn't matter which color you receive - they all increment your number just the same. If you send more to your friends, chances are you'll get more in return!
Read on for the full spoiler list of six rewards you can earn by collecting gems.
Blue Cave Pearls - 6 Gemstones
Purple Travertine - 10 Gemstones
Gleaming Skull - 16 Gemstones
Ceiling Crystal - 20 Gemstones
Longfin Damsel - 30 Gemstones