Tiles have health represented by a percentage.
Mining speed is determined by two factors: mining speed and mining power.
A tile's health is retained in the world (regen overtime?).
Ore tiles do not regen health and have more base health than other tiles.
The player has a certain amount of 'mining charges'.
The amount of charges determines how many tiles the player can mine before exhaustion can occur.
Once the player has mined more charges than the player has, there is an increasing chance for a mining charge to be exhausted each successive tile mined.
After a mining charge has been exhausted, the player now has a reduced amount of charges, and less blocks that can be mined before the next charge can be exhausted.
An exhausted charge can be refreshed by not mining for some time.
If the player exhausts all mining charges, the player can no longer mine and must wait a longer time before the next charge is refreshed.
For ore tiles, the charges can be exhausted not after so many tiles have been mined, but after so many hits to that ore tile.
? An ore tile might have a lower chance to exhaust a mining charge since they have more health and the chance activates every hit.