Final answer:
The materials that magma is made of are referred to as minerals. Minerals crystallize from magma as it cools, forming different types of igneous rocks with coarse or fine-grained textures, such as granite or basalt.
Step-by-step explanation:
The term that describes the materials magma is made of is c) "Minerals". Magma is essentially molten rock located beneath the Earth's surface and is comprised of various minerals, which crystallize as it cools to form igneous rocks. Depending on how quickly the magma cools, these minerals can form different sized crystals. Slow cooling rates allow larger crystal grains to form, which results in coarse-grained igneous rocks, such as granite if the crystals are lighter in color. Conversely, quick cooling rates yield smaller crystals, characteristic of fine-grained rocks like basalt. Granites, for example, can contain minerals such as quartz, feldspar, and mica, and display a sugary, sparkling appearance due to the flat crystal faces reflecting light.