The Rock Crusher and gray sand : Alternative to natural sand.

What is the Rock Crusher ?
A new kind of crafting station, that would transform gravel type blocks (Cobblestone, Cobbled deepslate, Blackstone, Basalt and Gravel) into a new sand type block : the gray sand. 

How it works ?
Like a furnace, we have to use fuel and the rock crusher will take time to transform blocks. 

They gray sand
An alternative sand (using old gravel texture from beta, but but slightly retouched)  to use some plants ( Sugar cane, cactus, bamboo,... ), craft concrete and TNT. But it can't be smelted into glass and used to make sandstone; as natural sand isn't renewable (if we forget wandering traders), my goal is to give an alternative to let us free to enjoy natural sand for building and decoration, but not to replace it. 

My thought.
I saw peoples suggesting to crush cobblestone into gravel, and gravel into sand like some mods. But It could make sense to make concrete with crushed rock, but not to make glass. This idea doesn't make renewable natural sand, but allows us to save natural sand for decoration or sandstone, and use this artificial renewable sand for concrete and TNT.

About the crafting recipe, I chose these materials for 2 reasons :

- We are talking about a machine that crush something hard like stone into sand, so it make sense if the machine must be hard.

- I don't want it to replace natural sand, but being an alternative. As cobblestone is really common and renewable, I don't want it to be accesible early and common, but like endgame stuff and precious.