21w07a introduced deepslate (grimstone) generating at deep places underground. However, if a lava pool generates at a low level, it will still be surrounded with stone.
Coords: /tp @s -4518 -57 20766
A screenshot is attached.
Lava pools inside grimstones do not generate grimstone around them.
Lava lakes replace grimstone with normal stone
Lava Pools Generate Regular Stone in Grimstone Caves
lava pool under y=0 is covered by normal stone instead of grimstone
Stone is still able of spawn even below level 0
stone generating around lavalakes below y0
Lava lakes generate stone under y0
Stone still generates under y=0
Lava lakes generating normal stone under y=0
Stone generating under y=0
Lava lakes replace Deepslate with stone
Lava Lakes don't update when in deep slate whilst the similar structures do
Stone generating around lava pools below 0
Underground lava pools under y=0 still generate with normal stone
some lava pits in deepslate layer generate with stone
Lava lakes always generate stone regardless of custom world generation settings