There are a lot of missing crafting recipes if Blackstone is equal to cobblestone and polished Blackstone is equal to stone. Here are the missing recipes:

Blackstone cannot craft:

• andisite
• diorite
• dispensers
• droppers
• Levers
• pistons
• Observers
• brewing stands

Polished Blackstone cannot craft:

• stonecutters
• repeaters
• comparators
• Blast furnaces

many of these items are necessary to survival in the nether, or at least to advance it.