The two main types of Igneous rocks are Intrusive which is the solidifying of magma under the earth's crust, and Extrusive which is the hardening of lava above the earths surface. An example of an Intrusive Igneous rock is Basalt which is a fine grained, dark colored rock composed mainly of material called plagioclase and pyroxene. An example of an Extrusive Igneous rock is Rhyolite, which is a light colored fine grained rock that usually contains quartz and feldspar minerals.
The two types of Metamorphic rock are Foliated and Non-Foliated rocks. Foliated rocks appear to have a layered or banded appearance that is produced by heat and directed pressure. Non-Foliated rocks do not have a layered or banded appearance. An example of an Non-Foliated rock is Amphibolite which forms through recrystallization under conditions of high viscosity and directed pressure. It is composed primarily of amphibole and plagioclase usually with very little quartz. An example of a Foliated rock would be Gneiss which has a banded appearance and is made up of granular mineral grains. It usually contains an abundant amount of quartz or feldspar minerals.
The two types of Sedimentary rocks are Clastic and Chemical. Clastic rocks consist of Breccia, Conglomerate, Sandstone, and Shale which is formed from mechanical weathering debris. While Chemical rocks such as rock salt and some limestones that form when dissolved materials precipitate from a solution. An example of a Clastic rock would be Shale which is made up of very small millimeter sized clay/weathering debris. It usually breaks into flat thin pieces. Rock salt is an example of a Chemical Sedimentary rock which form's from the evaporation or a ocean or saline lake waters. Also known as Halite, it is often used for chemical indusrty, highway treatment and as food seasoning.
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