Answer: Jadarite

In December 2004, researchers working for global mining corporation Rio Tinto Group discovered a mineral they couldn’t identify. They enlisted the aide of Dr. Chris Stanley (a mineralogist working at the Natural History Museum in London) along with Dr. Pamela Whitfield and Dr. Yvon Le Page (researchers from Canada’s National Research Council), and found they had discovered… Kryptonite.

The discovery was both literal and non-literal all at the same time. No, they hadn’t discovered the glowing green crystals that are iconic for their power to weaken Superman and Supergirl. But yes, they had in fact, discovered a mineral with a nearly identical chemical composition that writers had given to the fictional mineral in the 2006 film Superman Returns: sodium lithium boron silicate hydroxide—the only difference between the compound in the Superman film and the real life compound was the absence of fluorine.

If you’re a comic book fan and Superman aficionado, be prepared for disappointment: real life sodium lithium boron silicate hydroxide doesn’t glow, isn’t green, and its crystalline structure is so tiny that it looks more like a rock than a big dramatic crystal (but it will react to ultraviolet light by fluorescing a pinkish-orange).

The mineral derives its name, Jadarite, from where it was discovered: the Jadar River Valley in Serbia.