Which type of igneous rock is dark-colored and rich in iron and magnesium?

The correct answer is Mafic, as this term specifically refers to a group of igneous rocks that are dark-colored and have high concentrations of iron (Fe) and magnesium (Mg). Mafic rocks typically contain silicate minerals rich in these elements, such as pyroxene and olivine. Common examples of mafic rocks include basalt and gabbro, which display the characteristic darker color due to their mineral composition.

In contrast, felsic rocks, which are not the correct answer, are light-colored and contain higher amounts of silica as well as minerals like quartz and feldspar, making them generally lighter in appearance and composition. Granite, a specific type of felsic rock, is primarily composed of quartz and feldspar, further supporting its classification.

Olivine is a specific mineral that is commonly found in mafic rocks but is not a type of igneous rock itself. Therefore, while olivine contributes to the dark coloration of mafic rocks, it cannot be considered the correct answer in this context.