Rubinstien writes: A mineralogist at London's Natural History Museum was contracted to help identify an unknown mineral found in a Serbian mine. After its crystal structure was analyzed and identified, the researcher was shocked to find the material already referenced in literature. Says Dr. Chris Stanley, "Towards the end of my research I searched the web using the mineral's chemical formula — sodium lithium boron silicate hydroxide — and was amazed to discover that same scientific name, written on a case of rock containing kryptonite stolen by Lex Luther from a museum in the film Superman Returns." "I'm afraid it's not green and it doesn't glow either — although it will react to ultraviolet light by fluorescing a pinkish-orange," he told BBC News.
More details can be found in the BBC News article.