how do you know they're just retexture stone i might ask? but either way when RP2 world gen is on i get 40 FPS when its off i get 80+ FPS my system can handle the game no problem so something else is the problem.
Actually, I don't.
But they are blocks, not tile entity, and they only have a single texture, that can be changed via a texture pack with no trouble at all.
Knowing they don't have any function or special interaction, I would doubt that Eloram would go out off her way to code something special about them, apart from the worldgen part.
If you want to prove me that marble and basalt lag your game, here is an experiment you could do:
1. Make a custom flat world with 4 layers of stone and 1 of grass ( 4x1,2 ). write your fps after the world has loaded.
2. Make the same world, but with stone replaced by Basalt. ( 4x215:1,2 )
3. Make again the same world, with Marble this time. ( 4x215,2 )
For me, using un modified DW20 pack, default graphics options:
1. 125 FPS
2. between 124 and 126 FPS
3. 125 FPS
So I am sorry, these maps had a lot of marble, and a lot of basalt, because the render distance "far" does cause quite a lot to be generated and rendered.
I don't call my experiment a "proof" that it doesn't lag your game, but at least I proved it doesn't lag mine, not even by a single FPS, that's enough for me to keep them generate.