Gentlemen, if you’re looking for a nice rock to put on your lady’s finger, you might be on the wrong planet: scientists have hypothesized that on Jupiter and Saturn it may just rain diamonds, and form oceans of the stuff:
Astrophysicists have calculated that the conditions on the two biggest planets of the solar system are enough to produce stable oceans made from diamond.
They claim that powerful lightning storms in the planets’ atmospheres cause particles of carbon to form, which then drift down though the gas. As the carbon falls, it is crushed by the enormous pressures that exist on the two planets, causing them to form dense chunks of diamond.
At even greater depths, the scientists say the diamond will eventually melt to form liquid diamond, which may then form a stable ocean layer.
Full article: Diamonds May Fall as Rain on Jupiter and Saturn