Blue cobblestone is only obtained through mining. You can mine blue cobblestone at the Hub where there is only 1 spawn for the blue cobblestone. The blue cobble spawns every 3 hours.
Blue cobblestone has few uses in Scape craft, the main use for blue cobble is to make Blue cobblestone armour. The armour is purely cosmetic, the durability of the armour is very low and so it is suggested it is not used in combat.
When placing down a down a concentrated blue cobblestone, make sure you use a Silk Touch pickaxe because if you don't you will receive a blue cobblestone and in effect lose 8 blue cobblestone.
Blue Cobblestone ArmourEdit
Obtaining the blue cobblestone armour requires 216 blue cobblestone in all and is considered to be on par in terms of difficulty to obtain as lava armour. To create the armour you first need to place 9 cobble in a crafting table to create Concentrated Blue cobblestone. From concentrated blue cobblestone you can create the armour with the same minecraft armour recipes.