It's just a little bug. Close it down wait for a few minutes then try again, used to happen to me but now it's gone!
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The Efficiency enchantment makes you mine blocks faster.
Redstone blocks? You need an iron pickaxe.
You can use an iron, gold, or pre-existing diamond pickaxe to mine diamond ore or diamond blocks
You need to have the Silk Touch enchantment on your pickaxe, to be able to mine certain blocks instead of destroying them. With Silk Touch you can mine Ice, mine things like Diamond Ore instead of Diamonds, blocks of dirt with grass on already, etc.