Quallsite Crystal

The crystals found in The Glimmer around Quallsitte. These crystals have long been valuable to the people of Quallsitte for their natural ability to hold magic which strengthens the crystal from being very brittle to hard as diamond. This process gives the crystal an internal soft purple glow. While storing magic in these crystals makes them far more useful it is also a difficult and tedious process to cut the crystal in ways that allow it to hold the magic. The brittleness of the crystal in its growing form often causes it to shatter during the cutting process.
The people of Quallsitte use the crystal to make armor. Although less resistant than normal steel the armor is far lighter and has the unique property of allowing the user to draw upon the magic stored with. This makes the armor frequently sought after by mages, but the long process required to make the armor makes it outrageously expensive. (For gameplay purposes this would let some restore spell slots by filling the armor with a slot at a previous time.) 
The The Amethyst Tower was grown out of this crystal in such a way that it is able to hold a level of magic throughout the entire tower. This is what gives the tower its purple glow. Although it is unclear how all of this was done as the crystal has only ever been known to grow in The Glimmer and the exact magics used have been lost to history.
While the people of Quallsitte do make good money when trading the enhanced crystal works the amount of time required to make them and the quantity that the city itself needs has made the city unable to create a stable economy around trading the enhanced crystals. However the city has recently seen a massive economic boom and influx of immigrants looking to mine when it was discovered that the unenhanced brittle crystals could be used to power the Airship Engine. The trade of from harvesting the rapidly growing crystals has led to a lot more of the surface world to look upon the Depths Below with renewed interest.

Type

Ore/Mineral