Only 4 Refineries may work on a Crystal cluster at one time. The amount of crystals the cluster contains can be discovered by hovering over it.
Harvesting all of the crystals on a mission will earn the Efficient Medal, worth a bonus $500. If you do not harvest all of the crystals, you will scavenge 10% of whatever is left after the mission ends.
Extraction of Crystals can be enhanced with the following technologies and buildings: