Here's why:

* Rocks are naturally occurring solid materials.

* Minerals are naturally occurring, solid, inorganic substances with a defined chemical composition and crystal structure.

* Rocks are formed by the aggregation of one or more minerals.

There are exceptions to this rule:

* Some rocks may contain organic matter, such as coal, which is formed from fossilized plant material.

* Some rocks may contain glass, which is not a true mineral because it lacks a crystalline structure.

However, even in these cases, the majority of the rock is still composed of minerals.