NS3310 – Physical Science Studies Rocks and Minerals

Rocks Tell Stories Limestone Basalt Breccia Gneiss

Key Questions What is a rock? What is a mineral? What different kinds of rocks are there? How do rocks and minerals form? How can you tell them apart? Can one type of rock change into another type of rock? Can you tell the story of a rock by “reading” its characteristics?

The Story of Limestone Limestone forms by the precipitation of CaCO3 from solution in ocean water What is a solution? What is a precipitate? CaCO3 is an ionically bonded salt What is an ion? What is an ionic bond?

Ions Ions are atoms with more or less electrons than protons Complex ions can also form Ionic bonds form between ions due to their electrostatic charges Let’s learn more:

Most elements in the natural environment exist as ions

The Story of Basalt Basalt is formed from minerals crystallizing from lava at the earth’s surface Basalt is dense and mineral rich Basalt’s crystals are very fine-grained Basalt is the most common rock in the ocean floor

Distribution of Elements in the Solar System Elements in the Sun Carbonaceous Chondrites Elements in the Earth’s Core Elements in the Earth’s Mantle Elements in the Earth’s Crust Elements in the Earth’s Hydrosphere and Atmosphere

Minerals Chemical Composition Physical Properties Minerals are naturally occurring solids formed through geological processes that have a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties Chemical Composition Elemental Minerals Carbonate Minerals (and others with ionic bonds) Silicate Minerals (and others with covalent bonds) Physical Properties Crystal Structure Cleavage and Fracture Streak and Color Luster Hardness Specific Gravity Special Properties

What Holds Silicate Minerals Together? We’ve already seen that carbonate minerals form from ionic bonds, but what holds silicate minerals together? Silicate minerals are held together by covalent bonds Let’s learn more:

The Story of Granite Granite is an intrusive igneous rock Granite is composed of silicate minerals (feldspar, quartz, mica, and horneblende) Granite is coarse-grained because the crystals formed slowly Most of the earth’s continental crust is made of granite Most of this granite formed as intrusions into the earth’s crust

Igneous Rocks Intrusive Extrusive Pyroclastic Granite Diorite Gabbro Porphyry Extrusive Basalt Andesite Glass Scoria Obsidian Pumice Pyroclastic Tuff Rhyolite

The Story of Gneiss Gneiss is a metamorphic rock This means that it is altered from existing rock but was not completely melted The minerals in a gneiss have re-crystallized and formed light and dark bands due to heat and pressure exerted on the rock Gneiss has many stories

Rock Cycle Igneous rocks are formed from magma cooling in the earth’s crust or lava cooling on the surface. Sedimentary rocks are formed from the weathered pieces of existing rock. Metamorphic rocks are formed by the recrystallization of existing rocks. All rocks are susceptible to weathering and erosion. All rocks are also susceptible to metamorphism. All rocks can be subducted and re-melted (though the continents preserve rocks formed throughout earth’s history because they float higher in the mantle than do the oceans). The rock cycle is a continuous process!

You can Use Texture and Mineral Composition to Identify Rocks Igneous Rocks Intrusive Extrusive Pyroclastic Sedimentary Rocks Clastic Chemical Bioclastic Metamorphic Rocks Foliated Unfoliated

Types of Rocks Igneous Sedimentary Metamorphic Intrusive Extrusive Pyroclastic Sedimentary Chemical Precipitates and Evaporites Fossiliferous Clastic Sorted Unsorted Metamorphic Foliated Unfoliated

Sedimentary Rocks Sediment Formation Sediment Transport Mechanical and Chemical Weathering Sediment Transport Water, Ice, Wind and Gravity Sediment Deposition Weathering and Erosion Environment of Deposition

Clastic Sedimentary Rocks Unsorted Conglomerate Breccia Sorted Quartz Sandstone Arkose Graywacke Siltstone Shale

Chemical Sedimentary Rocks Precipitates Limestone Dolomite Travertine Chert Evaporites Gypsum Halite

Metamorphic Rocks Metamorphic Processes Regional Metamorphism Recrystallization Rotation Regional Metamorphism Contact Metamorphism Foliated Metamorphic Rocks Slate Phyllite Schist Gneiss Unfoliated Metamorphic Rocks Marble Quartzite

Key Concepts Minerals are naturally occurring elements and compounds in the earth. Rocks are combinations of minerals (or in some cases a single mineral) that form the earth’s crust. Rocks that form from magma, lava or pyroclastic material are igneous rocks. Rocks that form from sediments produced by chemical and physical weathering are called sedimentary rocks. Rocks that form by remineralization of existing rocks are metamorphic rocks. Processes that form and change rocks comprise the rock cycle. The characteristics of rocks tell their stories!