Well actually Rubanon, strictly speaking, isn’t on Earth as such. It’s a substance invented around 100 years ago, just after the start of the 22nd Century, by Professor Retnug Natiloportem (try saying that when you’ve had a half of Navah syrup).
She combined good old rubber with the element Memon (the hardest metal known to the human race) to invent Rubanon. This skin like material provides an incredibly hard yet flexible covering that can be used for a range of purposes, including as a very lifelike and hard wearing outer skin for robots.
Memon was discovered many years ago in our own Solar System, on Mars.