The Treasure Hunt is a new game mode that has been added to Gems of War with the Patch 1.0.6 (june 2015).
To play it you'll need a Treasure Map; once you managed to get one, go to Zhul’Kari and there you'll find the option to play this minigame.

Gameplay is very similar to the original mode:
Combine 3 or more same objects to get one of the next level and repeat. You have 15 turn to try your best, game ends after you've used them.
However, if you combine 4 objects together you won't lose any turn and you'll even get one extra turn if you combine 5 or more (this happens only once per turn: if you combine, let's say, 5 bronze coins and this let you combine 5 silver within the same move, you'll get only one extra turn, not two)

The evolution of the objects is the following:

low --------------------------------------------------------------------------------------> high




Please, notice that the can't be moved so maybe you want to make a bit more of planning before creating them.

When the match ends you'll be rewarded based on which elements you have on the table.
Every object will get you a little reward, randomly chosen between the followings:

• Every Bronze coin will give you 1 Gold;
  
• Every Silver coin will give you 3 Golds;
  
• Every Gold coin will give you 10 Golds;
  
• Every Sack will give you 25 Golds or 3 Souls;
  
• Every Chest will give you 65 Golds or 7 Souls or 1 Glory;
  
• Every Green chest will give you 175 Golds or 15 Souls or 2 Glory or 1 Gem;
  
• Every Red chest will give you 400 Golds or 35 Souls or 5 Glory or 1 Gem or 1 Key;
  
• Every Safe will give you 1000 Golds or 80 Souls or 10 Glory or 2 Gems or 2 Keys or 1 Magic key.

Thanks to GarrettChan for helping me complete this list.