Wormcrystal is material that can only be minded in the Battle sectors of the PvP-Area (the top row). Wormcrystal asteroids appear in one sector at a time, and only when the wormheart asteroids are not appearing in the lower two zones of the PvP-Area. Also, these asteroids appear for a limited time in a given sector, before disappearing.
Any wormcrystal mined can be sent back to your station through the outpost in the sector where the asteroids appear ... provided your faction controls that station. It takes 5 minutes to transfer a quantity of wormcrystal, so make sure your faction controls the station that long, or your mining efforts will be lost.