Rock Cycle

The two main types of igneous rocks are intrusive and extrusive. An example of an intrusive igneous rock is diorite. Diorite is a coarse-grained rock thats composition is made up of feldspar, pyroxene, hornblende, and occasionally quartz. Another example of an intrusive igneous rock is gabbro. Gabbro is a coarse-grained, dark colored rock thats composition is made up of feldspar, augite, and occasionally olivine. Examples of extrusive igneous rocks are rhyolite and obsidian. Rhyolite is a light colored, fine grained, and its composition usually contains quartz and feldspar. Obsidian is a dark colored volcanic glass that forms from quick cooling of molten rock material. It cools so quickly that crystals do not form, so it is very smooth.

The two main types of metamorphic rocks are foliated and nonfoliated. Two examples of foliated metamorphic rocks are slate and phyllite. Slate is formed through the metamorphism of shale. It is a low-grade metamorphic rock that splits into thin pieces. Phyllites composition is mainly very fine grained mica. The surface of phyllite is occasionally wrinkled. It has a intermediate grade of metamorphic. Two examples of non-foliated metamorphic rocks are marble and quartzite. Marble is produced from the metamorphism of limestone. It is mainly composed of calcium carbonate. Quartzite is produced by the metamorphism of snadstone. It is mainly made up of quartz.

The two main types of sedimentary rocks are clastic and chemical. Two examples of clastic sedimentary rocks are breccia and shale. Breccia is composed of large angular fragments. The spaces in the large fragments can be filled with smaller particles or a mineral cement which binds the rock together. Shale is made of clay size weathering debris. It usually breaks into small, thin, flat pieces. Two examples of chemical sedimentary rocks are rock salt and some limestones. Rock salt is formed from the evaporation of ocean or saline lake waters. It is also known by the mineraly named halite. It is used as a winter highway treatment. Limestone is calcium carbonate. It can form from the precitpitaion of calcium carbonate from lake or ocean water..