Kids learn about igneous rocks, such as serpentine; sedimentary rocks, such as shale; and metamorphic rocks, such as slate, in school. They also learn about common minerals such as calcite, gypsum, fluorite, limestone and quartz.
Igneous rocks form when molten rocks cool and solidify. The cooling rate determines the type of igneous rock that forms. If the molten rock, or magma, cools slowly, it forms coarse-grained rocks. If it cools rapidly, it forms small crystals and fine-grained rocks.Types of igneous rocks include andesite, basalt, granite and porphyry.
Sedimentary rocks form on land or in water as a result of accumulation of plant and animal material, rocks and minerals. Minerals and chemicals cement sedimentary rocks together, and they are held together by electrical attraction. Examples of sedimentary rocks are shale, conglomerate and sandstone.
Sometimes sedimentary rocks and igneous rocks go through changes after being exposed to extreme heat or pressure. When this happens, they form metamorphic rocks. These rocks do not melt to form new rocks. Instead, they transform into denser rocks. This may happen when fluids enter the rocks and react with the minerals or when the mineral components in the rocks rearrange themselves to form new minerals.
Minerals are inorganic solids that are formed by nature. Their chemical formula is very predictable, and they have a regular crystal structure. Some of their physical properties are hardness, luster, specific gravity, cleavage and structure.