It's a mode with 3 new ores as well as tools for 2 of them and armor for one of them.
Here is more detail of what it contains:
Games
Amber :
-Block
-Tools
Ruby :
-Tools
-Block
-Armor
Green Diamond:
-Block
In the future
-New Dimension
-World update : Structures, biomes etc....
-Useful control in games
-Added useful crafts
-etc......
