Rocks and Minerals: what's the difference?
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Rocks (and stones) are naturally occurring solids made up of minerals. There are three different types of rocks based on the way they form, igneous, sedimentary and metamorphic.
Geologist Devin Dennie heads to the kitchen to demonstrate the differences between the three types of rocks. Geology Kitchen
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Minerals are naturally occurring substances formed by geological processes. They are usually solid and feature a crystal structure as well as specific physical properties and chemical composition.
"To be considered a mineral, the substance must meet five criteria..."
A brief introduction to minerals with Michael Sammartano. |
The Three Kinds of Rocks"Rocks hold the history of the earth and the materials that will be used to build its future."
Information provided by Geology.com |
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Igneous
Igneous rocks are formed from the solidification of molten rock material. There are two basic types. Extrusive igneous rocks erupt onto the surface where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include andesite, basalt, obsidian, pumice, rhyolite, scoria, and tuff.
Intrusive igneous rocks crystallize below Earth's surface and the slow cooling that occurs there allows large crystals to form. Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite.
Key Words to Know
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Metamorphic
Metamorphic rocks have been modified by heat, pressure and chemical processes, usually while buried deep below Earth's surface. Exposure to these extreme conditions has altered the mineralogy, texture and chemical composition of the rocks. Foliated metamorphic rocks such as gneiss, phyllite, schist, and slate have a layered or banded appearance that is produced by exposure to heat and directed pressure.
Non-foliated metamorphic rocks such as hornfels, marble, quartzite, and novaculite do not have a layered or banded appearance.
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Sedimentary
Sedimentary rocks are formed by the accumulation of sediments. There are three basic types of sedimentary rocks. Chemical sedimentary rocks, such as rock salt, iron ore, chert, flint, some dolomites, and some limestones, form when dissolved materials precipitate from solution.
Clastic sedimentary rocks such as breccia, conglomerate, sandstone, siltstone, and shale are formed from mechanical weathering debris.
Organic sedimentary rocks such as coal, some dolomites, and some limestones, form from the accumulation of plant or animal debris.
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Useful Links
Vast resource for everything geology. http://geology.com/rocks/
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Mineral Identification | Mineralogy4Kids Four easy steps to identifying minerals
Great for supporting inquiry. |
Beautiful images of Rocks and Minerals from sandatlas.org
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