There are many different blocks in this game. This page will help you find any blocks you may be searching for. Each block is assumed to be 1 meter3.
You can find these in a non-altered world
Rocks - Aside from air, rocks are the most common block in the generated world and can be used for many low-tier tools. They are commonly found on mounatins, anywhere under the surface, and in Miners Paradise.
Grass - This block is very similar to dirt, but it makes up most of the top layer of dirt in the world.
Dirt - This block can be found in the first 2 biomes and occasionally underground.
Logs - Grows heavily in the Forest and Vertigo Forest biomes and is a necessary crafting item for making Wood. A critical item to have in the begining of a world so you can craft tools that require sticks.
Bloodstone - A blood red stone that is found near the hell world and helps create the strongest tools. Originally named Demon Skin in the original CastleMiner, it requires diamond tools to harvest. While mining beware of the Undead Dragon and Demons.
Lava - A "liquid" block that is confined to a cube form and has some amount of luminescence. It is dangerous to touch when they form a pool. Watch out for openings in the ground that can lead to the Hell world. It can now be mined with the higher-tier pickaxes after a new update (although it only drops rock).
Space Rock - A very useful material used for the crafting of ammo for Laser Weapons. Obtained by using a BloodStone PickAxe.
Space Goo - A material used for crafting Laser Weapons. Obtained by using a BloodStone PickAxe.
These must be crafted unless otherwise noted.
Copper Walls - These walls are used for crafting and for stronger protection against enemies. Created from 2 units of copper
Iron Walls - These walls are used for crafting and for stronger protection against enemies. Created from 2 units of iron.
Gold Walls - These walls are used for crafting and for protectionn against enemies. Created from 2 units of gold.
Diamond Walls - These walls are used for crafting and for protection against enemies, and are one of the strongest blocks to use as such. Created from 2 diamonds.
Lanterns - Technically, they are also a natural block, being found on the spawn tower, but as you can't mine them, they must be crafted. They are a powerful light block that can be made relatively cheaply.