I'll be streaming the first Saturday of October, mark your calendars today!
Geominer adds several new tiers of stone, ten to be exact, spanning from -300 to -3000 nodes. These added stones, and ores can not be broken with the tools Minetest_game provides, but rather you will need to find saplings and use explosives to get materials to craft tools that can break the new stones.
Watch out for falling cave ceilings, flash floods, and exploding gases.

More mods by this modder

It doesn't look like I've reviewed any other mods by this author, feel free to suggest one.