Which type of rock is primarily formed from cooling and solidification of molten material?

Igneous rocks are primarily formed from the cooling and solidification of molten material, which can be magma (when it cools beneath the Earth's surface) or lava (when it cools on the surface). The process of cooling allows the various minerals within the molten material to crystallize, leading to the formation of solid rock. This is a fundamental geological process, and the characteristics of igneous rocks can vary significantly depending on factors such as the cooling rate and the composition of the original molten material.

In contrast, metamorphic rocks are formed from existing rocks that undergo transformations due to heat and pressure, rather than from the solidification of molten material. Sedimentary rocks originate from the accumulation and cementation of mineral and organic particles. Finally, "mineral rocks" is a less standard term, as minerals themselves are the building blocks of all rock types, rather than a specific category of rock formed from molten material. Thus, igneous rocks are the correct answer as they are directly related to the cooling and solidification of magma or lava.