The correct grammar is actually: Polished Cracked Blackstone Bricks
Comments 3
Adjective order is:
Quantity or number.
Quality or opinion.
Size.
Age.
Shape.
Color.
Proper adjective (often nationality, other place of origin, or material)
Purpose or qualifier.
Followed by the noun. In this case, the noun is "bricks", and the qualifier is "blackstone". However, "polished" and "cracked" don't fit into any of these categories. Also, adjective order isn't even "proper" grammar, it's just a loose, emergent thing in language. so tl;dr Cracked Polished Blackstone Bricks is fine.
No? If you crack Polished Blackstone Bricks, you get Cracked Polished Blackstone Bricks. Polished Cracked Blackstone Bricks would be if you polished them after you cracked them, which you do not.