Wishstone

When someone makes a wish, whether good or ill-intentioned, somewhere in the Feywild, that wish coalesces into a small crystalline bit of potential. Brigganocks are instinctively drawn towards concentrations of these stones, and they dig mines in order to extract these enchanted minerals from the depths of the mountains.
Normally, wishstones appear as rough crystals that emit a soft, golden glow. They can be cut into valuable gemstones, but they then lose their glow and magical nature. They are often used as components in the construction of items that can grant wishes or grant luck.
Ill-intended wishes make the more sinister Dark Wishstones instead.