Mining Diamonds in Minecraft
Solution 1:
The iron pickaxe is fine for picking up diamond ore. So using your iron pickaxe for diamonds should work.
Have a look at this table :
Pickaxes
Even if the pickaxe loses it's durability you can take the next one and you will never ever lose ore for that. Either you pick it or you don't. Sometimes it happens that after mining the ore falls down into lava or water but that's it.