Minerals n What is a Mineral Enduring Understanding

Minerals n What is a Mineral?

Enduring Understanding n Minerals are the building blocks of rocks.

Minerals n Earth’s crust is composed of about 3, 000 different minerals. They play very important roles in civilization. Throughout history wars have been waged and empires have risen and fallen over the conquest of a select few minerals such as gold and silver considered to be precious.

Mineral Characteristics n Mineral is a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure n Naturally Occurring means they are formed by natural processes

Mineral Characteristics n Synthetic diamonds and other materials developed in labs are not minerals

Mineral Characteristics n Inorganic means that they are not and never were alive n Salt is a mineral sugar is not

Mineral Characteristics n Solid means it has a definite shape and volume n No liquids or gases n can be minerals!!!

Mineral Characteristics n n Specific Chemical Composition means that since most minerals are compounds, the elements and their proportions are unique to that mineral The chemical composition for Quartz is Si. O 2, with a chemical breakdown of approximately 46. 7% silicon and 53. 3% oxygen. Quartz is easily transformed from low to high quartz at 573 degrees Celsius with only minor atomic adjustments and without breaking any of the Si-O bonds.

Mineral Characteristics n Some minerals such as silver are found as a single element

Mineral Characteristics n Definite Crystalline Structure means the atoms are arranged in regular geometric patterns that are repeated over and over. n There are six major crystal systems:

Cubic

Tetragonal

Hexagonal

Orthorhombric

Monoclinic

Triclinic

Mineral Formation n Since minerals must form from natural processes there are two primary ways that they form here on Earth

Mineral Formation n Minerals can form from the cooling of magma which is the molten material found beneath Earth’s surface as magma rises closer to the surface the molten compounds no longer move freely and they begin to interact chemically to form minerals

Mineral Formation n Small crystals means the magma cooled rapidly

Mineral Formation n Large crystals means the magma cooled more slowly

Mineral Formation n Minerals also form from solution such as when a liquid evaporates from the solution and the elements remain behind “Evaporites”

Mineral Formation n Minerals will precipitate (drop out) of a solution that becomes supersaturated meaning it can hold no more dissolved solids

Mineral Groups n Of the 3, 000 minerals found in the crust only about 30 of these are common. Ten of these make up about 90% of the Earth’s crust

Mineral Groups n Silicates are the most abundant group (96%) containing the two most abundant elements in the crust Silicon (Si) and Oxygen (O)

Mineral Groups n Quartz and Feldspar are the most abundant minerals

Mineral Groups n Carbonates are minerals composed of one or more metallic elements with the carbonate compound CO 3

Mineral Groups n Calcite and dolomite are common examples

Mineral Groups n Carbonates are the primary minerals in rocks such as limestone, coquina, and marble

Mineral Groups n n Oxides are compounds of oxygen (O) and a metal. Hematite (Fe 2 O 3) and Magnetite (Fe 3 O 4) are common examples

Igneous Rocks

Endurung Understanding n n The rock cycle is an ongoing process by which rocks are formed. It gives us an explanation of how Earth materials are recycled through time. Virginia has many natural resources.

n Igneous Rocks Minerals combine in the Earth’s crust to form rocks. Most rocks are made of one or more minerals. Igneous rocks were the first type to form on Earth as its molten surface cooled and solidified

Igneous Rocks n Igneous Rocks form from the crystallization of magma

Igneous Rocks n Magma is molten rock below Earth’s surface

Igneous Rocks n Lava is magma that flows out onto Earth’s surface

Igneous Rock Types n n Igneous rocks are classified based upon where they form Extrusive igneous rocks cool quickly on the surface and are fine-grained (small crystals)

Igneous Rock Types n Rhyolite is the most common extrusive igneous rock

Igneous Rock Types n Other common extrusive igneous rocks include pumice, obsidian, and basalt

Igneous Rock Types n Intrusive igneous rocks cool slowly beneath the surface and are coarsegrained (larger crystals)

Igneous Rock Types n Granite is the most common intrusive igneous rock

Magma n Magma is often a slushy mix of molten rock, gases and mineral crystals. The elements in magma are the same major elements found in the Earth’s crust: oxygen (O), silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), and sodium (Na)

Magma n Silica (Si. O 2) is the most common compound in magma and has the greatest effect on its characteristics Rhyolitic magma has an Si. O 2 content of 70% n Andesitic magma has an Si. O 2 content of 60% n Basaltic magma has an Si. O 2 content of 50% n

Magma Formation n n There are four main factors that affect magma formation Temperature. Heat comes from the remaining energy from Earth’s formation and the decay of radioactive elements

Magma Formation n n There are four main factors that affect magma formation Pressure. The pressure increases with depth

Magma Formation n n There are four main factors that affect magma formation Water content. More decreases the melting point of the rocks

Magma Formation n Mineral content. Minerals melt at different temperatures

Classifying Igneous Rocks n Extrusive and intrusive igneous rocks are further classified by their mineral compositions

Classifying Igneous Rocks n Felsic rocks are light colored, have high silica contents, and contain quartz and the feldspars orthoclase and plagioclase n Granite is the most common felsic rock

Classifying Igneous Rocks n Intermediate rocks are darker than felsic and have moderate amounts of biotite, amphibole, and pyroxene n Diorite is a good example of an intermediate rock

Classifying Igneous Rocks n Mafic rocks are dark, have lower silica contents and are rich in iron and magnesium n Basalt is a mafic rock

Classifying Igneous Rocks n Ultramafic rocks have low silica contents and very high levels of iron and magnesium. n Olivine is an ultramafic rock

Bowen’s Reaction Series n As magma cools, minerals form in predictable patterns. The reaction series has two main branches of crystallization

Bowens Reaction Series

Bowen’s Reaction Series n As minerals form in the order shown in Bowens reaction series elements are removed from the remaining magma. Silica and Oxygen are the most abundant elements and are left over at the end of the reaction series. The remaining magma finally crystallizes to form quartz.

Bowens Reaction Series

Sedimentary Rocks

Objective 2. Classify sedimentary rocks by texture and composition. Ø Clastic – sandstone, conglomerate, and shale; Ø nonclastic – limestone and rock salt.

Sedimentary Rocks n The second classification of rocks includes many of the common types seen on the Earth’s surface. The native rocks found here on the coastal plain of Virginia are mostly of the sedimentary variety

Sedimentary Rocks n n Sediments are pieces of solid material that have been deposited on the surface by wind, water, ice, gravity or chemical precipitation http: //www. classzone. com/books/earth_sc ience/terc/content/visualizations/es 0604/e s 0604 page 01. cfm? chapter_no=visualizatio n

Sedimentary Rocks n Sediments are eroded and transported to new locations by four main agents: Wind, moving water, gravity, and glaciers

Sedimentary Rocks n n Deposition occurs when sediment transport ceases and they are laid down on the ground or sink to the bottom of water Sedimentary deposits are then buried in Sedimentary deposits are then layers called sedimentary basins from oldest to youngest n These basins can be as much as 8 km thick

Classification of clastic sediments n n n The sediments that form rocks can be classified according to the size of their particles > 2 mm – Gravel 0. 062 mm - 2 mm – Sand 0. 0039 mm- 0. 062 mm – Silt <. 0039 mm - Clay

Lithification n Lithification occurs as the temperature and pressure increases in the buried sediment and the physical and chemical processes transform the sediment into sedimentary rock

Lithification n The temperature in the crust increases by about 30 degrees per kilometer

Lithification n Cementation occurs when mineral growth cements sediment grains together into solid rock

Types of Sedimentary rocks The classification of sedimentary rocks is based on how they were formed. There are 3 main groups of sedimentary rocks

Types of Sedimentary rocks n Clastic sedimentary rocks are formed from the lithification of abundant deposits of loose sediments found on the Earth’s surface

Types of Sedimentary rocks n They can further be classified according to their particle size n Course-grained clastics consist of gravel-sized rock and mineral fragments

Types of Sedimentary rocks n Conglomerate and breccia are examples

Types of Sedimentary rocks n Medium-grained clastics consist of sandsized particles n Sandstone is a medium-grained clastic rock

Types of Sedimentary rocks n Fine-grained clastics are made of silt and Fine-grained clastics are made of clay sized particles n Shale is an example

Types of Sedimentary rocks n Chemical sedimentary rocks form through processes such as evaporation when bodies of water become oversaturated with solids.

Types of Sedimentary rocks n Crystal grains will precipitate out of the solution and settle to the bottom to form layers of chemical sedimentary called evaporites

Types of Sedimentary rocks n Rock salt is formed this way and the main source of the table salt we use every day

Types of Sedimentary rocks n Organic sedimentary rocks are formed from the remains of once-living things.

Types of Sedimentary rocks n These rocks form in the oceans and as the organisms die their shells settle to the bottom form thick layers of sediment over geologic time.

Types of Sedimentary rocks n Eventually these layers of sediment can undergo lithification and become solid rock

Types of Sedimentary rocks n Limestone is our most common organic sedimentary rock

Types of Sedimentary rocks n Coal forms when the remains of plant material accumulate in swamps and coastal areas. These layers are buried and compressed over millions of years and become lithified

Metamorphic Rocks

Objective 3. Classify metamorphic rocks by texture and composition. Ø Foliated – slate, schist, and gneiss; Ø Nonfoliated – marble and quartzite.

Metamorphic Rocks n When high pressure and temperature combine to alter the texture, mineralogy, or chemical composition of a rock without actually melting it, then the third classification of rocks form metamorphic

Metamorphic Rocks n n During metamorphism the rock changes while remaining in the solid form http: //www. classzone. com/books/earth_sc ience/terc/content/visualizations/es 0607/e s 0607 page 01. cfm? chapter_no=visualizatio n

Metamorphic Rocks n The temperatures required come from Earth’s internal heat

Metamorphic Rocks n The high pressures required can be generated from either vertical pressure from the overlying rock or from the compressive forces as rocks are deformed

Types of Metamorphism n Different combinations of temperature and pressure result in different types of metamorphism

Types of Metamorphism n Regional metamorphism occurs when high temperature and pressure affect large regions of the crust

Types of Metamorphism n Plate movements and mountain-building results in regional metamorphism

Types of Metamorphism n Contact metamorphism occurs when molten rocks come in contact with solid rock.

Types of Metamorphism n An igneous intrusion causes many instances of contact metamorphism

Types of Metamorphism n Hydrothermal metamorphism occurs when very hot water reacts with rock and alters its chemistry and mineralogy

Types of Metamorphism n Yellowstone National Park gets its name from this type of geologic activity

Metamorphic Textures n Foliated metamorphic rocks have wavy layers and bands of minerals

Metamorphic Textures n Slate, schist (shale) and gneiss (granite) are the two most common types

Metamorphic Textures n Nonfoliated metamorphic rocks are composed of minerals that form with blocky crystal shapes; no layers and bands

Metamorphic Textures n Quartzite (sandstone) and Marble (limestone) are common examples

The Rock Cycle n Rocks are not as immortal as one may think. The three rock classifications igneous, sedimentary, and metamorphic are constantly changing under the geologic conditions and recycling themselves becoming other forms

The Rock Cycle n Igneous rocks break down under chemical and physical weathering on the surface to form sediment that can then undergo lithification and form sedimentary rock.

The Rock Cycle n n Any rocks that melt again become igneous rocks and may re-crystallize in a completely different combination of minerals. http: //www. classzone. com/books/earth_sc ience/terc/content/investigations/es 0602/e s 0602 page 02. cfm

The Rock Cycle

The Physiographic Provinces of Virginia n n Virginia has had a long, complex geologic history, over 1. 1 billion years Events that have led to the formation of a rich diversity of rocks, and events that have folded, faulted and rearranged those rocks in complex patterns. A physiographic province is a landform region, areas divided according to similar terrain that has been shaped by a common geologic history. Geographers recognize more than 20 physiographic provinces in North America; five of these are in the state of Virginia.

The Physiographic Provinces of Virginia n Each province is characterized overall by its elevation, relief, lithology, and geologic structure. Because of the region’s history of rock formation, deformation, and erosion, specific types of landforms or other geologic features may be associated with a given province.

The Physiographic Provinces of Virginia

Coastal Plain � The Coastal Plain is a flat area underlain by young, unconsolidated sediments. � Includes all of Virginia East of the Fall Line. � The Fall Line is where Rivers cross from the hard igneous and metamorphic rocks of the Piedmont onto the soft roundest rocks in Virginia. � Deposits of sand, silt and clay including marine fossils deposited by rivers. � Layers of sediment were produced by erosion of the Appalachian Mountains and then deposited on the Coastal Plain.

Coastal Plain

Piedmont � The Piedmont is an area of rolling hills underlain by mostly ancient igneous and metamorphic rocks. � Igneous rocks are the roots of volcanoes formed during an ancient episode of subduction that occurred before the formation of the Appalachian Mountains. � Largest physiographic province. � Bounded on the east by the Fall Zone, and on the west by the mountains of the Blue Ridge. � Rolling topography, deeply weathered bedrock and rocks are strongly weathered. � Rocks are generally buried under a thick (2 -20 m) blanket of saprolite. ( a chemically weathered rock) � Topography is more rugged closer to the Blue Ridge.

Piedmont

Blue Ridge � The Blue Ridge is a high ridge of crystalline rock separating the Piedmont from the Valley and Ridge Province. � The billion-year old igneous and metamorphic rocks of the Blue Ridge are the oldest in the state. � The Blue Ridge province experienced mountain building during the late Neoproterozoic era (750700 Ma). � In central and northern Virginia, the 570 million year old basalts are over sedimentary rock. � Some metamorphism of these rocks occurred during the formation of the Appalachian Mountains.

Blue Ridge

Valley and Ridge � � � Long parallel ridges and valleys of sedimentary rock which were folded and faulted, and eroded differently. 540 million years old sandstones are overlain by carbonates that make up a region of limestone and dolomite. The folding and faulting of the sedimentary rocks occurred during a collision between Africa and North America. The collision, which occurred in the late Paleozoic, produced the Appalachian Mountains. Carbonates were deposited in a shallow tropical ocean along the southeast edge of North America. Carbonates in the Shenandoah Valley create the correct environment for caves and sinkholes (Karst Topography)

Valley and Ridge

Appalachian Plateau � The Appalachian Plateau has rugged irregular topography and is underlain by ancient, flatlying sedimentary rocks. � Large folds of rock found in the Valley and Ridge become smaller folds and flat-lying rocks in the Plateau. � Some parts of the Plateau are relatively flat, and some are hilly and rugged. � The area is actually a series of plateaus separated by faults. The upper layers of the Plateau are rich in mineral resources like coal, natural gas, and petroleum.

Appalachian Plateau