Salpetre mine

The Salpetre Mine counts as a building.

Prerequisites

You need to prospect the underground (preferrably hills) outside the capital. (I'm not sure about this)

You can only build a Salpetre Mine on a square where you discovered a deposit of salpetre. (I'm not sure about this)

Costs

The construction of the building requires 1 political point, 1,500 gold, 50 wood and 50 tools.

Benefits

The Salpetre Mine can employ up to 100 workers.

It produces 1 salpetre per worker per year.

Remarks

Even if the storage (for salpetre ) in the city is full, the workers continue to empty the reservoir. (I'm not sure about this)

Once the deposit is exhausted, the mine is destroyed. (I'm not sure about this)

You can have not more than 4 subterranean buildings (mines or quarries) in a province.