Seconding what @simone54 and @hiphiphopflipflapflop said and “rock” is a funny thing for a planet to be made of.
So: “In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.” which could be just about anything. 49.5% (by mass) of our planet’s crust is oxygen (as part of rock)...
@frigate1985 Lead doesn’t necessarily settle to the bottom, it depends on the evolution of the planet. (That is, if the lead was deposited on the planet after it cooled, it could stay on the surface)
The “wood or paper that doesn’t burn” is an odd thing. Sounds to me like a mineral fiber? The reason that just about all organisms are flammable is that combustion is simply a fast oxidation reaction. We use oxidation to produce energy, so it’s possible to make that sort of thing happen fast. If it doesn’t burn, you’re probably talking about something like a mineral fiber? http://en.wikipedia.org/wiki/Mineral_wool
One thing to look for maybe is the chemical makeup of asteroids—they are sort of the “raw building blocks” that planets are made from—the ratios of elements in asteroids are typical of the generation of solar system we have. Heavier elements- -anything heavier than Hydrogen & Helium (which were produced in the big bang)—are all produced during the course of stellar evolution, and some only produced in supernova. Anything heavier than Oxygen (e.g., the Iron in your blood) is produced in a supernova. That means that your lead, your Argon, etc. are all super rare in the universe.