I remember in high school chemistry class one of the experiments was moving around the room, burning different minerals in Bunsen burners and guessing what the mineral’s composition was based upon the colors of the flames. The colors were surprisingly vivid and I was enchanted. Strontium containing compounds burned bold red, Calcium a jack-o-lantern orange, Potassium a pleasant violet of nearly magenta, Green from a number of chemicals (though if I recall properly we used copper sulfate. No promises, though, that was a while ago). Blue is easy to see from a simple alcohol flame. It’s like fireworks, but though explosions in the sky are fun for me it’s the fire on the ground, close enough to touch but for the fact it would hurt you that is more enticing. Most of these colors you have to deliberately create – we don’t often see them occurring in the natural world, at least where visible to many of us.

Which is what makes the Ijen volcano in Indonesia so entrancing. The flames from the lava are a brilliant, pure blue. Though it’s not the lava itself that causes this – it’s the concentration of sulfur gases also flowing forth from the volcano.

Exposed to the oxygen present in air and sparked by lava, the sulfur burns readily, and its flames are bright blue. There’s so much sulfur, Grunewald says, that at times it flows down the rock face as it burns, making it seem as though blue lava is spilling down the mountainside.

Imagine though, if you walked through a world where extreme concentrations of various minerals caused explosions of colorful flames. Or perhaps a group has to find their way through a desolate landscape, and have to follow the path of a specific kind of mineral that burns a specific otherworldly color. It’s a fantasy after all, so you can kind of do what you want. My favorite fantasy worlds though, are those that take the incredible from what we know occurs and expands upon it.