Rocks are formed in three primary ways, and each method produces rocks with different characteristics. Rocks are either classified as sedimentary, igneous or metamorphic, depending on the manner in which they were formed... More »

Metamorphic rocks are formed due to physical and chemical processes, such as heat, pressure and mineral exposure, that change the composition of pre-existing igneous, sedimentary and metamorphic rocks. These processes ma... More » Science Earth Science Geology

According to the National Park Service, sedimentary rock forms when mud and sand are deposited into layers on the earth’s surface and later buried. The buried mud and sand is compacted by the weight of the overlying laye... More » Science Earth Science Geology

Igneous rocks are formed when melted lava or magma cools and crystallizes, and their unique traits are based on this process. They are strong because their mineral grains grow together tightly as they cool, and their min... More »

Sedimentary rocks are characterised by their formation from the deposition and lithification of rock material. They may be formed through physical and chemical processes, such as mechanical weathering, compaction and dis... More »

Silica is a compound that occurs in rocks and minerals in the form of silicon dioxide, SiO2. It can be found in quartz, flint and sand. It is used to make glass, ceramics and concrete. More » Science Earth Science Geology

Igneous rocks that are allowed to cool more slowly form larger crystals, while igneous rocks that cool quickly form smaller crystals. It is simply a matter of time. The longer it takes for magma to cool, the more time is... More »