Silt Block

Silt is the main pre-Hardmode shortcut to ores your world did not give you, along with gems and coins, once you own an Extractinator. If you are mining below the surface anyway, collecting it costs nothing and pays out later. Stockpile now, process it when you have the machine.

It falls, so let gravity do the collecting. Dig out the block holding a column up, and put a torch or a length of minecart track underneath first: a falling block that lands on one of those pops into item form instead of settling as terrain, so the whole column ends up in your inventory rather than needing to be mined a second time.

Falling silt hurts whatever is underneath it, which makes it usable for crude traps, and it fills lava the way sand does. Unlike sand it will not carry corruption, crimson or hallow, so a silt barrier holds a line that a sand one would not. The one caveat is the moment Hardmode begins, when any silt caught inside the new biomes converts along with everything else. After that it stays put.