ICE

No villager trades ice, and no wandering trader carries it. That puts it in a small group of blocks with no price at all: it has no crafting recipe either, so the only way to own a block of it is to take one out of the world yourself.

The Mason is the villager who sells building blocks, and his sheet is stone, brick, terracotta and quartz. Frozen blocks were never part of it. The Wandering Trader covers the odd natural block instead, plants and saplings and the occasional coral, and ice is not among his rolls.

What ice does give you is the fastest surface in the game once it is packed: 9 blocks of it press into a single packed ice, which no longer melts and is what most ice roads are actually built from.

Breaking a block of ice with a normal tool gives you water, not the block. The block only survives the break with silk touch. That single rule is why an ice road is a project rather than an afternoon: every block in it had to be mined with the right pickaxe and carried home.

A Librarian is the practical way to that pickaxe. An enchanted book names its enchantment before you pay, so buying the right book beats gambling at an enchanting table for it.

Boats on ice are the fastest ordinary travel in Minecraft, quicker than sprinting and quicker than a minecart on level ground. A tunnel of it between two villages turns a long walk into a short slide, which matters when a trading hall is not next door.

Keep the plain kind away from torches and lava. It melts near light, and packing it into packed ice removes that problem entirely, which is why long roads use the packed version and keep the clear blocks for decoration.

Plain ice melts near a light source, which is the first thing anybody discovers by putting a torch next to it. Pack nine into a block and you get packed ice, which does not melt at all, and that is the version worth building with.

Mining ice without Silk Touch leaves you with water rather than a block, so the pickaxe decides whether a frozen lake is a resource or a puddle.

The reason to care is speed. Boats on ice are the fastest travel in the game short of an elytra, and packed or blue ice under a boat turns a corridor into a rail line with no rails in it.

No trader offers plain Ice, but it is the one you can grow yourself: water under open sky in a cold biome freezes over, and How to Build an Ice Farm in Minecraft turns a pool into a farm. Crafted 9 at a time it becomes Packed Ice, which the wandering trader does sell.