stone is kinda silver and light gray (gray or grey???) , blackstone is black and purple , deepslate is metalic silver black.
blackstone is hardest to find , deepslate is not hard to find but hard to mine!
next time you go mining specialy making a strip mine or a tunnel underground, make sure to keep these blocks.
and i thing its a bug that cobbled deepslate can be directly used to make deepslate bricks and ... using stonecutter.
Fun fact: using stone cutter to make stairs will cost you 1/3 less than crafting.
final answer: deepslate
