Limestone

It only makes sense to add a block as beautiful as limestone to the game because as in real life situations the water and liquids that seep into caves in real life caves dry and cling to the limestone creating the stalagmites and stalactites that we see generated in your Minecraft caves and i heavily believe you can make the lime stone be found in what points on mountains and the bases of the stalagmites and stalactites that we find in our beautiful and wonderful Minecraft cave biomes.