You can't really mine for gems,but there is a 1 out of 250 chance when your mining for anything.you might find a gem.
This is what your mining for!Ore is used for making different types of armor and weapons.When you mix certain types of
ore you will get a metal bar.
Bronze ore:Minimum Level-1
Tin ore:Minimum Level-1
Iron ore:Minimum Level-15
Mithril ore:Minimum Level-55
Adamantite ore:Minimum Level-70
Runite Ore:Minimum Level-85
There are other things that you can mine other than ore or gems.
Silver:Minimum Level-20 (for more information,look in the crafting section)
Gold:Minimum Level-40 (for more information,look in the crafting section)