Minecraft wiki entry for Smelting, associated text: The following additional ores can be smelted, but it's more efficient to mine them with an appropriate pickaxe. Mining them saves fuel and in most cases yields more product and experience, especially if the pickaxe has a Fortune enchantment. Smelting them, though, allows obtaining them from an automatic device. The ore blocks themselves can be obtained only via the Silk Touch enchantment.