DIORITE

Diorite is a raw-material trade: villagers pay emeralds for it, which makes it a candidate for an automated emerald farm rather than something you purchase back.

Diorite is a building block. The Mason offers polished and processed stone variants that would otherwise need a stonecutter and raw materials to produce.

Only the Mason deals in it, so any trading hall that supplies Diorite is built around that one profession. Diorite can also be obtained outside of trading, but buying it from a villager is often faster than gathering or smelting the ingredients yourself.

To sell Diorite for emeralds, bring it to a Mason at the Journeyman tier (16 units per 1 emerald).

On the supply side, Diorite is worth one emerald per 16 units at its best rate (the Mason). That ratio is what decides whether farming diorite for currency is efficient: the fewer units a villager demands per emerald, the more valuable each one is to produce. A buy slot like this can be used 16 times before it locks and the villager has to restock, capping how many emeralds one villager returns per cycle before it must work at its job site again.

Since no villager sells diorite back, this is a one-way emerald faucet: you supply the diorite, the villager supplies the emeralds. That makes it a prime candidate for an automated trading hall, where a renewable source of diorite feeds a row of villagers and steadily converts your surplus into currency you can spend on the gear and rare items other professions sell.

Every Diorite trade follows Minecraft's standard supply-and-demand rules. A trade can be used a limited number of times — 16 for the slot in question — before it greys out and locks until the villager restocks. A villager restocks up to twice per in-game day, but only if it can path to its job-site block and "work" there, which is why a trading hall must leave the workstation reachable.

When you sell diorite to a villager, completing that trade is what grants the villager career experience and pushes it toward its next tier. Spreading sales across several villagers of the same profession multiplies both your emerald throughput and how quickly the hall levels up.

One caution: the first trade you complete with a fresh villager permanently locks its current offers, including the diorite slot at whatever price it rolled. If you are chasing a specific price, decide before you trade, because there is no re-rolling a villager once it has done business with you.