New requirement~

[Yunfa]

You need to finish Tundra Exploration Mission under 20 minutes to unlock mines, anybody want to form a party? I can't solo it...

[jooozek]

I should add that you also need also to achieve S-Rank.

[Priest]

I should add that for free mines you need to srank mines 2 and 3 with 18 and 22 minutes respectively, and you also need 2 planet drops which you should get from your first 5 mobs in mines 2 or 3.