Topaz Gemcorn

A gemcorn is an acorn with a gem pushed into it, and it grows a tree of that gem underground. Cutting the tree down returns stone, some gems and usually a few more gemcorns off the leafy branches, so a plot can keep itself stocked. Planting is one way. Once it is in the ground you cannot take the gemcorn back, and breaking the sapling gives you nothing at all.

The conditions are fussier than a normal sapling.

• It has to be below the surface layer, on stone, with mossy and biome variants allowed, and at least one block next to that stone must also be stone.
• No liquid in the sapling's tile or in the tiles immediately either side of it.
• The lower half of the sapling needs its background clear, apart from a short list of walls it tolerates, fences included.
• It needs a tall clear column above it, wider than the sapling itself, containing nothing but other saplings. Less headroom does not stop growth, it produces a shorter tree more slowly.

Light is irrelevant, so a sealed unlit room is fine.

Leave three tiles between saplings. Any tighter and branches crowd each other out, any wider and you are wasting wall. Gemcorns refuse to plant on hammered blocks, so hammering the stone in the gaps physically prevents misplacement, and smart cursor gets you the same result with less setup.

Because the farm sits underground it will spawn enemies unless you wall it in, and fences are on the list of walls a sapling accepts, which lets you cover the whole plot without breaking anything.

Label the rows. Gem torches or a Topaz Gemspark Block under each sapling tells you what is planted where. Paint works too, but a gemcorn planted on painted stone grows a painted tree, which fights the very gem color you were trying to read. Illuminant Coating is the better answer, since it makes the tree and its gems readable in complete darkness.

Fertilizer on a legal sapling skips the wait entirely and pops a finished tree on the spot. Infused Fertilizer demands far more vertical room than a normal farm provides, so it will simply refuse on a standard layout. Left alone, a gem tree needs a bit over a day of game time.

Yield swings enormously from tree to tree. Every trunk, branch and leaf tile rolls on its own, so one tree hands you a fistful of gems and the next gives nothing but rubble. Barren branches, the plain grey ones with no gem leaves on them, never return a gemcorn, which is where most of the variance comes from. Judge a farm across dozens of harvests rather than one, and expect stone to be the bulk of what you carry out.

You can plant on mossy stone, but moss growths poke into the sapling's space and block it. Clear the moss under a sapling before the tree goes up, because once it has grown the moss underneath cannot be removed at all.

A gemcorn sells for what its gem is worth, so nothing is lost by shimmering spares apart, selling the gems and keeping the acorns for the next batch. In a Skyblock world the trees are worth planting for the stone alone, with surplus gems going toward anvils that shimmer back into more stone.