What Is a Rock?

Good question!



They are two entirely different things.

Rock is what our planet's crust consists of - it is an essential component of the planet Earth.

 

It is solid and it consists of minerals, other rock pieces, sometimes fossils, and rarely, a mass of glass.

By definition, it is coherent, which means it holds together and must be broken to be separated into pieces; and as opposed to some minerals, it is always naturally occuring - not manufactured like concrete or brick.

In a nonglassy rock (which are the most rocks), the grains are stuck together either because they interlock with each other, or by natural cement - mineral material that percipitates from water and fills the space between grains.