Crystals are one of the two most rare items to obtain in FarSky. You will need a Drill to mine them.
They can be found on the bottom layer, and look like Stone "Pillars", with cyan strips in them.
Every Crystal deposit comes with 2 or 3 Crystals, and is defended by at least 3 Krakens.
The Krakens are passive, but as soon as you attack them or mine the Crystal Ore, they will become hostile and Attack you
Use / CraftingEdit
Crystals are needed to craft to following items:
The best way to get Crystals safely is to take a Spear Gun with good Spears (at least Copper).
Now make sure that there are no annoying enemies around you, such as Predators or Jellyfishes.
Once you have placed the Cannon, start fighting the Krakens in range of your Cannon.
If all Krakens are dead, you can simply mine the Crystals.