Here's a breakdown:

* Igneous rocks are formed from the cooling and solidification of magma (molten rock) or lava.

* Minerals are naturally occurring solid substances with a specific chemical composition and crystal structure.

* Mineral composition refers to the types and proportions of minerals present in a rock.

This is why igneous rocks are classified into two main groups:

* Felsic rocks: Rich in silica (SiO2), potassium, sodium, and aluminum. They typically have light colors (e.g., granite, rhyolite).

* Mafic rocks: Rich in magnesium, iron, and calcium. They typically have dark colors (e.g., basalt, gabbro).

There are also intermediate and ultramafic rocks, which have varying proportions of these minerals.

While other factors like texture (grain size) and cooling rate play a role in classifying igneous rocks, mineral composition is the primary chemical property used to distinguish them.