Rubies

Rubies are the premium currency that can be used in Pocket Mine.

There are a few ways to obtain rubies: ​
 * You can purchase them in packs with real money (via In-App Purchase)
 * You can earn some by inviting your friends to the game.
 * They have to get the game and login through Facebook for you to get your reward.
 * Note that the reward for inviting friends is not always rubies.
 * ​You can randomly get a few from opening chests.

Uses
There are many uses for rubies, since they are the premium currency.

Here is a list of some things you can purchase with rubies:
 * New characters for use in expeditions.
 * Card packs.
 * New factories in the factory menu.
 * Speed up crafting in the factory.
 * Re-rolling cards at the beginning of an expedition.