Thanks a lot for helping me decide the job I want, engineer all the way.

Set iron-ore to minimum 100 and normal 500. Say the only resource tile under a miner has an amount of 1000.
Now the miner will output one iron ore each mining cycle until it has mined 500 iron ore. At this point, the yield value will slowly. E.g., after another 250 iron ores, the resource tile has ...