There are three main ways to get coal. The first two you'll get are the Coal Furnace and Deep Mining upgrades at the workshop. These will let you get small amounts of coal for each mine (0.003 per tick, 0.015 per second) and running smelter (base .005 per tick, .025 per second).
But, by far the best source of coal, is unlocking the Geology technology, and assigning Kittens to the Geologist job. Geologists are worth .015 coal per tick , equivalent to three smelters, or five mines. And kittens can improve at their jobs; a Master Geologist is earning about 0.026 coal per tick, which is over 0.1 coal per second each.
There are also quarries, which each give a +35% boost to mineral production, as well as another 0.015 coal per tick. They won't improve on their own the way Kittens improve their skills, but they still help a lot.
There are also several upgrades at the workshop related to coal which can help. Pyrolysis will increase coal gains by 20% from all sources. The Geodesy will increase Geologists' base coal per tick to 0.0225, making even a Dabbling Geologist worth four and a half Deep Mining mines. It also allows Geologists to produce a small amount of gold while they work.
In an Iron Will run, the resources that kittens normally gather are obtained thusly:
- Catnip: Fields or trade.
- Wood: Refinement or trade. As a bonus, Lumber Mills' effect boosts the return from refinement in Iron Will.
- Science: Astronomical events. As a bonus, Iron Will runs always have at least a 25% chance of these auto-succeeding, even without observatories. Remember that science buildings boost the reward from these.
- Catpower: Zebras will help you hunt. Each zebra is worth .15 Catpower per second.
- Minerals: Meteors will still fall. As a bonus, meteors are more common in Iron Will mode, and are also worth 10% more. Remember that mines do boost the reward from these.
- Gold: Once you have the Gold Ore upgrade, Zebra hunters have a 25% chance to obtain gold. Also, the usual rate of gold gain from Smelters is still available after that same upgrade.
- Maximum Catpower: Each upgrade to Catpower (bolas, hunting armour, etc.) will increase this, since you can't normally boost it without housing. Composite Bows make the maximum 200, Bolas make the maximum 400, and Hunting Armor gives you exactly 1000 max (before Paragon and the like) so you can discover people to trade with.
- Faith: Chapels will be your only source of faith while playing in Iron Will mode.
- Coal: Quarries will still provide coal. So will Smelters, after getting the Coal Furnace upgrade.
Also, although Zebras' hunting abilities are enough to get Unicorns, because max Catpower is so limited early on, there is a slight chance every tick of a Unicorn simply showing up at your village, as long as you are in Iron Will mode, have Archery, and have less than two unicorns already.
Best Answer
Iron is produced by Smelters from Minerals and Wood. Smelters can be built once you've discovered Metal Working. You also need to research Construction to unlock Iron.