Rocks are classified as igneous, sedimentary, or metamorphic based primarily on their origin and formation process. Here's a breakdown:

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

* Sedimentary rocks: Form from the accumulation and cementation of sediments, which are fragments of other rocks, minerals, or organic matter.

* Metamorphic rocks: Form when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are transformed by heat, pressure, or chemical reactions.

While mineralogy and texture can provide clues about a rock's classification, the origin is the defining factor.