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.