I can't get anything after mining Diamonds in Minecraft

I have found a HUGE diamond, gold, and redstone cave and every time I mine each one it just destroys it with nothing in return. I am using my Iron Pickaxe, play on the lowest difficulty, and just recently bought the game. This is very confusing and fustrating for me. Is this a glitch in the game or am I doing something wrong?

In my experience, Mincraft: XBox 360 Edition can be a little glitchy about placing blocks, rendering lighting, and sometimes mining. But I haven't seen it this bad. Generally restarting Minecraft, or rebooting the XBox, will help the game perform better.

So, I would restart the XBox and try again. If this fails, I might try crafting a new iron pickaxe, but that's just a guess.

If you can't get diamonds by mining them, it's probably because you're in Creative Mode. In order to obtain them, you need to switch to Survival Mode. If you break blocks in Creative Mode, you won't get the reward.