Grass Block

Grass Block is dirt with a living surface, and the distinction matters more than it looks. Mining one gives you plain dirt unless the tool carries Silk Touch, which is the only way to pick up a grass block and keep it as one — the grass is a state that spreads, not a material you can craft.

It spreads on its own from a Grass Block to any dirt beside it, a level up or down, as long as enough light reaches the dirt and nothing opaque is sitting on top of it. The rule runs backwards too: cover a Grass Block with a solid block, a slab or deep water and the grass dies back to dirt. That is how to turn dirt into grass without hauling one anywhere — put the dirt next to grass, light the area and wait — and also why the floor of a covered building slowly goes brown.

Bone meal on a Grass Block grows short grass and whichever flowers belong to that biome, which makes a lawn a flower farm as well. A hoe turns it into farmland and a shovel turns it into a dirt path, both of which strip the grass for good. Animals need grass to spawn on, so paving a field is what stops sheep and cows appearing there, and leaving it intact inside a pen is what keeps sheep in wool.

The top texture is tinted by biome rather than fixed, so the same block reads green in a forest, murky in a swamp and pale in a savanna, and one carried between biomes takes the color of wherever it ends up. A layer of snow on top turns the sides white, which is all a snowy grass block is: the same block wearing snow, not a separate one to collect.