They are part of a quest that can be obtained from Jeremiah the Iron Worker in the secure area of the Prism of Light. The quest is called "Crystalline Fragments". You will need to collect 10 Crystalline Fragments, and in return you will receive a Craftsman's Satchel.
Last but not least, they are a nice light source when locked down in a house.
...So I tried this and locked some down, it got dark, they did nothing... ???