We just learned that rocks are made up of minerals, and that minerals are the building blocks of the world.
One type of mineral is called pyrite.
It is a shiny metal that looks so much like gold that people called it fool's gold because people would discover it and think they had real gold and were rich.
The metal pyrite is actually made up of iron and sulfur combined together.
(from: wikipedia - pyrite)
Kid Facts - Blast from the past: Acceleration