In 2061: Odyssey Three, one of the sequels to 2001: A Space Odyssey, the human race discovers an endless supply of diamonds on Jupiter. Carbon, being one of the most common elements in the universe, probably is abundant on Jupiter, and Jupiter, along with the other gas giants, would exert such tremendous amounts of pressure on that carbon that it could form diamonds.
By the end of the Space Odyssey series, diamonds are so common that they’re used as an ordinary construction material. Not for decoration, but for strength. Diamond windows, for example, are far less breakable than old-fashioned glass.
A recent study has shown that Uranus and Neptune really could produce diamonds. In fact, these planets have the right internal pressures and temperatures to form vast oceans of liquid diamond, with solidified chunks floating like icebergs on the surface. Far stranger and more wonderful than what Arthur C. Clark envisioned in his books.
Now we just have to figure out how to get there and how to extract these diamonds safely. It might even be possible, if these diamond oceans really exist, to collect the liquid, mold it, and produce diamonds in any shape we want.
In other news, scientists have discovered a planet 4000 light years away that is one giant diamond. This planet was once a star, but all it’s stellar material has burned off, leaving a huge lump of compressed carbon—there for the taking.
One thing is clear: when the day comes that space travel is safe and cheap, diamonds will not be quite as valuable as they are today. The universe has lots of carbon and lots of places where that carbon is under extreme pressure. Diamonds are everywhere.