|Gem Type||Rarity||Expected # of
Days to Obtain
|1/500,000||5.79 Days||This cannot be sold|
|1/25,000,000||289 Days||This cannot be sold|
Every Gem (except blood crystals) will upgrade tools in the order above. Upgrading tools is much more valuable than selling them to the NPC market. To collect the gems that he finds, you have to click on him periodically, to see if he has found a rock with a gem inside. If you have the tier 4 mining research perk, you can skip this step, because he will automatically collect what he finds.