IRON INGOT

Three separate professions buy iron ingot, an Armorer, a Toolsmith and a Weaponsmith, and unlike most items sold to more than one buyer, all three quote the exact same 4-to-1 rate. Whichever of them you find first is worth exactly as much as the other two.

A crafting grid makes one from nine iron nuggets, itself smelted from raw iron, so anyone mining or farming iron already has the ingots on hand before a villager ever enters the picture; the trade mostly matters for turning a surplus into emeralds rather than the other way around.

Several buyers, one price: an Armorer at apprentice, a Toolsmith at apprentice, and a Weaponsmith at apprentice all pay 4 iron ingots for 1 emerald, the same figure repeated across every trade file that mentions iron ingot.

The best rate any villager offers is an emerald per 4 iron ingots, from the Armorer, and 2 of the other 3 pay out faster. No villager sells iron ingot back, so it is emeralds out and nothing in.

One slot at the Armorer takes 4 iron ingots a trade, 12 trades, 12 emeralds. 8 of the 72 villagers that pay emeralds, emptied out:

12 acacia boats against 288 paper for the same 12 emeralds, 24 times the carrying, and the shortest wait is the Butcher at 7.5 real minutes of shelf, gathering not counted. Iron Ingot itself pays 4 an emerald, so 13 of the 72 ask less and 50 ask more.

Every iron ingot offer locks after 12 uses, and a villager restocks at most twice a Minecraft day, so 24 of these trades caps one villager before the day, not your patience, stops him.

It surfaces at level 2 of 5 on all three professions, reached at 10 trade experience. A freshly employed one of any of the three is 1 tier short of offering it.

48 iron ingots fill one slot at any of the three, and each needs 2 real minutes back at work before buying again. A Minecraft day, 20 real minutes, covers two of those refills.

A full day at any one of them nets 96 iron ingots off your hands for 24 emeralds. A stack of 64 takes more than one fill of the slot.

Any of the three clears 12 trades for 12 emeralds before locking, and since all three pay the same, the nearest villager of the three is the right one to sell to. Where the emeralds go back: the same Armorer also sells chainmail boots, his cheapest offer.

The rest of the Armorer's sheet, worth a look on the same trip: bell, chainmail leggings, lava bucket, chainmail helmet, chainmail chestplate and shield.

Iron golems drop ingots, and a village that has enough villagers and beds keeps producing golems, which is why an iron farm is usually the first automatic thing a player builds. That makes iron the one metal you can have in bulk without mining for it.

Almost every tool chain runs through it: buckets, shears, anvils, rails, hoppers and every piece of iron gear. Nine nuggets make an ingot and nine ingots make a block, so trades that pay in ingots are easy to compare against a farm's output.

Tools and armour are the obvious use and not the expensive one. Hoppers are five ingots each, rails are six for sixteen, a minecart is five, an anvil is thirty-one counting the blocks, and a full redstone build swallows more iron than a set of armour ever will.

Nuggets are the other direction: one ingot gives nine, and nuggets are what lanterns, chains and the golden versions of things are built from.

Iron also rusts in a sense. Left as ore it is nothing; smelted into ingots it stacks, and nine stack into a block, which is the only sensible way to store the output of a farm that never stops.

The Armorer, the Toolsmith and the Weaponsmith all buy Iron Ingots, 4 to the emerald, and together they take 144 before any of them restocks. Nobody mines that for a handful of emeralds; an iron farm makes it while you do something else. How to Build an Iron Golem Farm in Minecraft 1.21 and How to Build an Iron Farm in Minecraft both walk through one.