Frozen Fire

Frozen Fire.
This is called such by the natives for obvious reasons: its brilliant orange hue and ability to glow in the dark make it a rare-but-effective method of lighting. Local legend has it that they are the remains of the first fire given to man. After using it to burn the forests down, the gods took it and hid it in the Earth, where the cold made it shrivel and freeze.
As a matter of fact, the truth is much less interesting. Inside the crystals are the hibernating specimens of primordial microorganisms. Any contact with oxygen revitalizes them, and they make their presence known by emitting a powerful bioluminescent display. This phenomenon is so rare that, up to this day, only one community in the entire world has a deposit. Due to security reasons, they refuse to divulge where the mine actually is, so the secret remains safe in the Earth.

Rendered in Blender 2.6