Emerald

"Ah, to be minted with the green stuff. To swan about the villages of the Overworld with pockets bursting with emeralds. “Ho there, villager!” you would bellow, tossing a few emeralds for a handful of carrots. You’d never need farm again!"

- Alex Wiltshire

Emeralds are rare minerals, and are used in trading or to power beacons. They are obtained from ores, which are the rarest type in minecraft

Trading
Emeralds can be obtained by trading with villagers, since they are the currency that villagers use for trading. Villagers either buy or sell specific goods for emeralds.

Mining
Emerald ore drops one emerald when mined using an iron or better pickaxe. If the pickaxe is enchanted with Fortune, it may drop an extra emerald per level of Fortune, up to a maximum of 4 emeralds with Fortune III. If the ore is mined using a pickaxe enchanted with Silk Touch, it drops itself instead of an emerald.

Drops
Vindicators and evokers drop 0–1 emeralds upon death. Looting increases the maximum emerald drop by one per level, for a maximum of 4 emeralds with Looting III.

Foxes that are holding emeralds also have a chance of 8.5%/100% to drop the emerald they are holding upon death. Alternatively, the player can drop a food item to induce the fox to drop the emerald.

$$, vindicators and pillagers spawned from raids can drop 0–1 emeralds. Depending on difficulty, vindicators and pillagers spawned from raids also have a chance of dropping additional emeralds. There is a 65% chance of dropping on easy and normal, and an 80% chance of dropping on hard. If this additional drop condition is met, different emerald counts can drop with different chances. There is a $10/39$ chance to drop an additional 0–1 emeralds, a $5/39$ chance to drop an additional 2–3, and a $2/39$ chance to drop an additional 4–5.

$$, with Looting III, it is possible for a vindicator in a raid to drop up to 16 emeralds upon death (vindicator drops + raid drops + an additional drop).

Trading
Emeralds are primarily used as currency for trading with villagers and wandering traders. Trading is typically a faster way to obtain emeralds than by mining, as emerald ore is very rare.

Beacons
Emeralds can be used to select powers from a beacon. The player must select one of the available powers and then insert an emerald into the item slot.

An emerald can be substituted for an iron ingot, a gold ingot, a diamond or a netherite ingot.

Trivia

 * The ruby was going to be the villager currency but was changed to emeralds before the update's release.