Final answer:
The three most common rock types are igneous, sedimentary, and metamorphic, with metamorphic rocks being the ones that have transformed from another type due to heat and pressure, such as marble from limestone.
Step-by-step explanation:
The three most common types of rocks are igneous, sedimentary, and metamorphic rocks. Igneous rocks, such as basalt, obsidian, and granite, form from the cooling and solidifying of magma or lava. Sedimentary rocks, like sandstones, shales, and limestones, are made from fragments of other rocks or organic material that have been cemented together. Among these, metamorphic rocks were once another type of rock—either igneous or sedimentary—but were changed due to heat and pressure.
These transformations result in new textures and mineral alignments, or foliation. Examples of metamorphic rocks include schist, slate, and marble. Each metamorphic rock originates from a protolith or parent rock; for example, limestone can metamorphose into marble.