Nikolite is a dust that looks a lot like redstone, but is cyan. It is mined from Nikolite Ore that looks pale blue. It is used for making Blue Alloy Ingots and Blue Doped Wafers. Anything that produces or uses Blutricity requires Nikolite to create them.
Nikolite is also an excellent source of EMC. It's extremely common, and has a relatively high EMC value (128) considering how easy it is to find tons of it. Each stack is worth a diamond.
It is also affected by Fortune enchantments, meaning you can get far more out of ores with such a pickaxe.