Minecraft wiki entry for Cobblestone_farming, associated text: If you plan to use an iron or diamond pickaxe, the blocks should be obsidian. Otherwise, you can also use an ore besides coal or nether quartz, or you can use a mineral block besides coal, quartz, or redstone. Iron ore and gold ore can be obtained without the silk touch enchantment.
If you plan to use a stone pickaxe, exclude iron ore, lapis lazuli ore, block of iron, or Lapis lazuli blocks.