First of all, cobblestone is the best block in the game.
Second of all, like mining, cobblestone is and has always been the cornerstone of all skyblock (Even public minecraft skyblock servers like manacube (Wow)).
Lastly, I am in the process of making a cactus farm (as some unnamed mod(s) may have seen (I found a few signs and a rather altered landscape on my island :/ ?)) so most of the cobble gets deleted by the cactus.
Also, everything I said to Wings applies to you too.
Be kewl, mine cobble. There's a fine line between being funny and being a meanie.