It appears to some that Superman's 'Fortress of Solitude' has been discovered, but it doesn't exist in the arctic rather it was found in a cave a 1000 feet below Naica Mountain in the Chihuahuan desert in northern Mexico.  The cave is filled with giant crystal beams that range close to 40 feet in length and weigh up to 55 tons each.  According to National Geographic the crystals are composed of translucent gypsum.  Until recently, the cave was filled with water that remained at a near constant 136 degrees Fahrenheit thanks to underground magma and at that temperature the mineral anhydrite, which is present in abundance in the water, turns into gypsum.

While the haphazard arrangement of the crystals doesn't resemble the ice cathedral look of the Man of Steel's northern retreat, it does look remarkably like the destroyed 'Fortress of Solitude' in Superman 2.  As the Technovelgy Website pointed out, this discovery might not quite as compelling if it were not for a near contemporaneous find in a mine in Jadar, Serbia, where an unknown mineral was analyzed and found to have a rare chemical formula, 'sodium lithium boron silicate hydroxide.'  When Dr. Chris Stanley, a mineralogist at London's Natural History Museum who analyzed the unusual rock, searched the chemical composition of the rock on the Internet, he came up with lots of hits, but the matches were with the formula written on a box containing Kryptonite in the movie Superman Returns not with any articles in geological journals.