GeoStrata

GeoStrata is a small mod to diversify underground world generation, making mining and caves more interesting, while simultaneously adding many aesthetic and functional building materials.
Its basic premise is that it adds a bunch of real-world rock types which overwrite 10-20% of vanilla stone. These rocks generate at realistic depths, and in realistic biomes (for example, shale and limestone, being silt/mud rocks, spawn more often in oceans, and cannot spawn in deserts). These stones cannot overwrite ores, nor do they block ores from spawning.
GeoStrata cobble can be used as vanilla cobble for use in properly-coded recipes.

Not all rocks are created equal; some are harder to mine and require better pickaxes. However, these ones also have greater blast resistances, with granite and hornfel being the hardest to destroy. Soft rock like shale is the most easily destroyed.

GeoStrata rock behaves like vanilla stone with pickaxes - it generates as smooth stone, drops cobblestone (unless using silk touch), can be smelted into smooth, and smooth can be crafted into bricks. A variety of other designs are also craftable.

GeoStrata also generates vents in the floors of caves, including under bodies of liquid. Vents are normally dormant, but occasionally fire for a few seconds, emitting sound, particles, and giving various effects.

Vents come in six types, some of which are dangerous:

• Steam vents emit white smoke particles and deal 0.5 hearts of damage per second to mobs standing on them
• Smoke vents emit black smoke and deal no damage
• Fire vents emit flames and light mobs on top of them on fire, plus dealing 1 heart of damage per second
• Lava vents emit lava particles and deal 4 hearts of damage per second, in addition to lighting mobs and blocks on fire
• Gas vents emit potion particles and deal an area-of-effect poison potion effect
• Water vents emit splash particles, hurt endermen, and extinguish burning entities

All vents generate naturally in stone, with fire-type and gas vents occurring deeper underground. All vents also respond to redstone, and will trigger when given a positive edge. They can only be harvested with Silk Touch.

Some vanilla blocks can also be crafted into brick variants, but keeping their original properties, like redstone, glowstone, and obsidian.