Got this off of io9...
New Evidence For Seas of Liquid Diamond On NeptuneRemote gas giant planets Neptune and Uranus could be covered in vast seas of liquid diamond, dotted with solid diamond chunks like icebergs. A new experiment revealed such oceans are plausible, and would explain some oddities about Neptune's magnetic field.
Published recently in Nature Physics, the study is an effort to explain two things: What causes the magnetic poles of Neptune and Uranus to be so far off their geographic poles; and what would cause the planets to have a 10 percent carbon makeup. Diamond seas are the answer, and their experiment suggested that these seas would behave a lot like water oceans.
I love stories like this... they prove how wonderfully strange the universe can get