Saturn's moon Titan features mountains made of water ice hard as rock and seas of liquid natural gas, with beaches darkened by organic soot.

https://spacedaily.com/j-v-on-titan-the-mountains-are-made-of-water-frozen-so-hard-at-nearly-minus-180-degrees-that-it-behaves-like-rock-while-the-seas-are-liquid-natural-gas-and-the-black-beaches-are-soot-drifting-down-fro/