Mirrorlight

Mirrorlight is a crystal which generally only forms on the peaks of mountain ranges and other extremely high up locations. Its formation is closely related to stormy weather and the electrical ozone which comes with the territory. Its appearance has numerous cracks and breaks within it, showing the immense energy stored within.
Slightly unstable, it's a crystal which has few uses outside of destruction. Despite being formed under electrical conditions, it has a very small threshold of impact force before the crystals violently explode. It is infrequently refined, as the cost of error is extremely high. Theorized to come from a connection to the heavens, when it is refined it amplifies the connection to the divine within the wielder and acts as a potent focus for divine magic.
Mirrorlight is relatively unique in that it is a growable crystal. It has an extremely high crystallization rate, as well as conditions that can be replicated through magical means. As a result, Mirrorlight farms exist on many domesticated mountains, rapidly growing these valuable crystals.
Mirrorlight weaponry and traps exist, however they are relatively rare to due the difficulty in refinement. As a result, one-time usage explosives are their more common use in the veins of combat as it drastically reduces the cost of use.