Any ore that generates below y=0 when surrounded by tuff blocks generates the stone variant.

How to replicate it:

21w08a - diamond ore visible outside of the tuff

21w08b - Redstone ore within the tuff

Creative mode(obiviously)

Seed: 3326623431520428958

Teleport to 523, -50, -151 or travel to there. It didn't load when I teleported, so instead, I traveled. The tuff is surrounding the redstone ore. Break a few blocks to reveal the stone variant of the ore below y = 0.

 

All photos are taken in snapshot 21w08b, but the world for the diamond ore was generated in 21w08a. The last redstone ore photo is from the 21w08b generation.