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• 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
– 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
– Intrusive– Extrusive– Pyroclastic
• Sedimentary– Chemical
• Precipitates and Evaporites• Fossiliferous
– Clastic• Sorted• Unsorted
• Metamorphic– Foliated– Unfoliated
Sedimentary Rocks
• Sediment Formation– 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
– 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!