1. Origin (how they formed): This is the most fundamental way to categorize rocks.

* Igneous rocks form from the cooling and solidification of magma or lava.

* Sedimentary rocks form from the accumulation and cementation of sediments.

* Metamorphic rocks form when existing rocks are transformed by heat, pressure, or chemical reactions.

2. Mineral composition: The types and proportions of minerals present in a rock are crucial for its classification. Different minerals give rocks their unique properties like color, texture, and hardness. This is especially important for igneous and metamorphic rocks.

By considering both origin and mineral composition, geologists can accurately classify rocks into various types.