You can earn diamonds in several ways:

1. By collecting Free diamonds once a day in the Shop;

   

2. By buying them;

3. By completing sawmill missions;

   

4. By completing missions;

   lumber pass

   

5. By participating in limited-time events;

    

6. By accumulating diamonds in the piggy bank and breaking it. 

   

7. By receiving Mr. Bill Mark manager, who gives you 3 diamonds every 4 hours.