Mining almost done

right now I'm working on the mining method.
(only in survival)
Basicly how it will work is:

1.You tell the Admin what you want to mine.
2. You roll the d20.
3. If the roll is equal or more of the minimum you roll the specified die to see how many you can add to your inventory.


(ex.
player:I want to mine some diamonds
player makes sure he has a iron or diamond pickaxe
player rolls d20 and gets a 17 (minimum is 16)
player rolls a D4
player gets a 2
player adds 2 diamonds to character sheet
)

After i'm done with mining I will work out how long until you can mine diamonds, iron, etc again (we don't want people to have 100 diamonds because they were lucky :)