mud - soil with mud, muck, or mire; The child mucked up his shirt while playing ball in the garden muck up, muck, mire begrime, bemire, colly, dirty, grime, soil - make soiled, filthy, or dirty; don't soil your clothes when you play outside!
Quartz is one of the most common minerals in the Earth's crust. It is made up of silicon dioxide (SiO2), otherwise known as silica. White sand is primarily made from quartz. Click here to find out more.
Most of the iron is in the core of the earth. Most of the oxygen is locked up in minerals with silicon. In fact, the mineral quartz is made up of only silicon and oxygen. The inner planets are relatively small and mostly solid, though earth has a thin atmosphere made up mostly of nitrogen and oxygen gases.