UNIT 9TOPIC 11 IN REVIEW BOOK

ROCKS, MINERALS & NATURAL

RESOURCES

I. Minerals

•Minerals are the building blocks of rocks!

•A mineral is a naturally occurring, inorganic solid with identifiable characteristic properties.

A. Properties of Minerals

1. Color:the most obvious and least reliable property.

2. LUSTER•The way in which a mineral reacts to light

•Metallic…shines like a metal•Nonmetallic…Can be glassy, dull, earthy, pearly…

3. HARDNESS

•A measure of a mineral’s ability to scratch or be scratched

•The reference most used is glass with a hardness value of 5

•Hardness is the most reliable identifying characteristic

4. CLEAVAGE/FRACTURE

•If a mineral breaks along a plane of weakness,

it shows cleavage and will have one or more smooth, flat surfaces

•If a mineral does not have a plane of weakness,

it will break irregularly and have one or more jagged edges

                                                

                                                

5. STREAK

•The color of the powdered form of a mineral

•It is determined by rubbing the mineral on an unglazed porcelain plate

                                                

Rock-forming Minerals

•The 20 to 30 common minerals that make up most rocks

•The most abundant rock-forming minerals belong to thesilicate group

Silicates

•Are made up of the elementssilicon andoxygenin some combination

•Silicon and oxygen bond together with a structure called asilicon-oxygen tetrahedron

•The physical properties of a mineral are due to

the internal arrangement of atoms

II. ROCKS

•A rock is any naturally formed solid on Earth or in the Universe.

•Rocks are distinguished and identified based on their composition and texture

•The texture of a rock is the size, shape and arrangement of the materials that comprise it

•Rocks are made up of one or more minerals.

•Monomineralic rocks are made up of only one mineral

•Polymineralic rocks are made up of two or more minerals

•Rocks are classified based upon

how they are made… their origin

•There are three types of rocks:

1.Sedimentary2.Metamorphic3.Igneous

A. SEDIMENTARY ROCKS

1. Most are made of solid fragments of sediments (called clasts) that have been weathered from other rocks and are called clastic sedimentary rocks

•These rocks form from an accumulation of sediments on or within the top few kilometers of Earth’s crust. They are classified based upon the size of their sediments

•These sediments combine to create rocks through:– burial, compaction, and/or cementation

•Minerals such as calcite, quartz and/or hematite are the common cements holding sediments together

2. Some sedimentary rocks are made of intergrown or interconnecting mineral crystals and are called crystalline sedimentary rocks

•These rocks form when the minerals dissolved in water precipitate or evaporate out of solution forming a crystalline mass

3. An organic, sedimentary rock is formed by living organisms or is mostly composed of materials from life forms…example: fossils!

B. METAMORPHIC ROCKS

•Rocks that form from changes in previously existing rocks due to exposure to heat and pressure (without melting)

•The process through which the changes occur is called metamorphism.

•These changes typically occur within the lithosphere many kilometers beneath the surface

•The resultant rock is generally less porous and more dense than the original rock (parent rock).

•They also have larger, or distorted crystals and frequently show a layering of mineral crystals called foliation

•Metamorphic rocks are classified and identified based on composition and texture

1. Contact metamorphism occurs when older (pre-existing) rocks come into contact with the magma of an intrusion or the lava of an extrusion

•At zones of contact metamorphism there is a gradual progression from the igneous rock to metamorphic rock to parent rock without clear separations.

•Metamorphic rocks such as hornfels, marble and quartzite are formed at these zones. Because heat is dominant over pressure, these rocks usually are not foliated

2. Regional metamorphism occurs when sections of the lithosphere (called plates) converge, the rocks are exposed to high temperatures and pressure causing mountain-building and resulting in the creation of metamorphic rocks

C. IGNEOUS ROCKS

•Igneous rocks are rocks that form when natural, molten rock-forming material cools into a solid.

•Magma is liquid rock beneath the surface of the earth

•Magma becomes lava when it exits onto the earth’s surface

•Igneous rocks were the first rock type to form because the earth was mostly molten at its formation.

•All igneous rocks are the result of solidification.

•Depending upon the location (and therefore, the rate) of solidification crystals of varying sizes may form.

•The size of the crystals formed is directly dependent on the amount of time the molten material takes to cool.

•The longer the period of cooling, the larger the crystals

1. Intrusive Igneous Rocks

•An igneous rock is intrusive (plutonic) when the magma cools beneath the surface of the earth.

•Intrusive igneous rocks cool slowly due to the temperature and pressure beneath the earth’s surface … providing ample time for the formation of crystals.

•These rocks are characterized by large, intergrown crystals easily visible to the human eye

2. Extrusive Igneous Rocks

•A rock is extrusive (volcanic) when the magma cools at or near the surface of the earth.

•Extrusive igneous rocks cool very quickly due to the lower temperature and pressure of the earth’s surface … providing little time for crystal formation

•These rocks have very small crystals and are said to have a fine texture orthey have no crystals at all and are said to have a glassy texture

•Many of the extrusive rocks formed from lava flows or volcanoes have rounded openings formed around trapped, expanding gases.

•They are said to have a vesicular texture

Identifying Igneous Rocks

•Igneous rocks are identified on the basis of texture and percent mineral composition

TEXTURE

•based on size of crystals – the rate of cooling– Coarse: large, visible crystals: intrusive

– Fine: small, indiscernible crystals: extrusive (near the surface)

– Glassy: no crystals at all –looks like glass: extrusive (at the surface)

–Vesicular: contains air pockets from escaping air – often compacted volcanic ash: extrusive (at the surface)

MINERAL COMPOSITION

•FELSIC: igneous rocks high in Aluminum and Silicon–Quartz and Potassium Feldspar are the key minerals

–Tend to be light in color and low in density

•MAFIC: igneous rocks high in Iron and Magnesium–Pyroxene, Olivine and large amounts of Plagioclase Feldspar are the key minerals

–Tend to be dark in color and high in density

                                                 

      

                                                

                                                

                                                

                                                

                                                

III. Rocks and Environment of Formation

•The type of environment in which a rock is formed can be inferred from its composition, structure and texture

•Large, thick areas of rock salt in western NYS lead us to the inference that, in that region, there was a large, shallow area of salty water that has evaporated

•The bent and twisted rock structure of the surface metamorphic rocks of the Adirondack region in northern NYS indicate that this region once experienced one or more periods of mountain building processes …

as well as uplift and erosion that exposed the rocks that formed deep beneath the surface

•Sharp, angular sediments in a clastic sedimentary rock indicate that the rock was formed close to where the sediments were created. They also indicate that the area may have been covered by a glacier

•Smooth and well rounded sediments in a clastic sedimentary rock indicate that the rock formed far from where the sediments were created. Long-distance transportation of sediments round and smooth them.

IV. THE ROCK CYCLE

•A model that indicates the method of formation as well as the interconnectedness of each type of rock

•Any rock can be changed into any other rock type.

•There is no preferred direction of movement around the rock cycle

•There is no exact point of separation between the rock types

•The driving forces of the rock cycle are–energy from the earth’s interior

–insolation from the sun–gravity

•These forces create the processes of uplift, erosion, weathering, pressure and high temperatures

V. NATURAL RESOURCES

•Natural resources are the things that people need that come from the earth.–Such as: water to drink, air to breathe, plants to eat and use for shelter, animals to provide food and clothing, energy

A. Renewable Resources

•Those resources that can be replaced by natural processes at a rate that is approximately equal to the rate at which they are used

•Resources that are replaceable within a human lifetime

•Although renewable resources may not run out, their usage may be limited by how quickly the resource is created

•Examples: drinking water, plants, trees, soil, oxygen, fish, electromagnetic energy from the sun

B. Nonrenewable Resources•Resources that exist in fixed amounts. If they are formed in nature, they are formed so slowly that their use will decrease their availability.

•They are not replaceable within a human existence

•There is a limited supply of these resources.

•Examples: minerals, rocks, metal ores, fossil fuels.

•Fossil fuels include oil/petroleum, natural gas, coal and oil shale

•and are the result of the compaction and organic chemical changes in large deposits of organic sediments which are the remains of dead plants and animals

Mineral characteristics and their use

1. Quartz vibrates in a regular fashion making it useful in watches

2. Minerals with a high hardness are used in jewelry and as abrasives.

3. Talc is very soft and has cleavage in one direction making it easily powdered and feel smooth. This makes it used in cosmetics and baby and foot powders.

4. Graphite is very soft with a black streak making it useful as the main ingredient in pencil “lead”

5. Hematite’s red color was been used in cave paintings and is used in cosmetics and red paints

Rock characteristics and their use

1. Slate is impermeable and breaks along foliations to produce thin, flat pieces to be used for roofing and chalkboards

2. Basalt resists crushing so it is used as a base under roads and railroad tracks.

3. Pumice has natural pore spaces and a low density making it useful as a building insulator and an exfoliator!

4. Granite and quartzite are very resistant to weathering so they are used as building stones.

5. Coal can burn and produce energy

Rock characteristics and landscapes

•Areas high in limestone and dolostone often have numerous caves and sinkholes due to their ability to be easily dissolved and weathered. The weathering of limestone produces nonacidic soils good for crops.

•Regions high in shale often have low topography with a rolling landscape and gentle slopes because shale weathers and erodes easily.

•Regions high in gneiss and granite are structurally sound allowing for the development of high-rise buildings and sky-scrappers.

THE END!