Identifying Igneous Rocks
Igneous rocks are one of the three main classifications of rocks, and they are formed both above and below ground. Learn about the intrusive and coarse-grained nature of igneous rocks with help from a lab manager and research scientist in this free video on identifying rocks.
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Hi this is Jane Stammer from the Colorado School of Mines and I am here to answer questions on how to identify an igneous rocks. Igneous rocks are one of the three classifications of rocks. They are formed both below ground and above ground. When they are formed below ground they are called intrusive rocks and they are typically coarse grained. When they are formed above ground such as an lava flow as you would see in Hawaii they are called extrusive rocks and they are typically fine grained. This is a basalt which is an extrusive igneous rock. It is very fine grained and you can see there are little holes in here where air pockets once were. This is from an ancient lava flow in Colorado and you can see these types of rocks all over the world most notably in Hawaii and other island settings. Depending on the chemical compositions of igneous rocks they can be both light in color and dark in color and that is how to identify an igneous rock.