UNIT II Rocks, Minerals, & Resources Mineral Display at American Museum of Natural History in NYC Presentation created by Mr. Elliott from Fort Plain Central School. Modified by Mr. Oliver Summer 2012.
Start Unit II Objective Page Don t forget to leave a column for dates. #1. What are minerals and describe their characteristics? #2. Describe properties of minerals including the seven basic physical properties of minerals. (ESRT p.16)
Lithosphere Introduction includes crust and small portion of upper mantle Made of solid materials called rock. Building blocks of rock are called minerals.
Rocks composed of single mineral called monomineralic. Rocks composed of many minerals called polymineralic. Polymineralic Rock Monomineralic Rock Rock Salt (made of halite only).
A. Minerals *Mineral: Naturally formed material made up of one or more elements. In order for a material to be a mineral it must be (have): Naturally occurring Crystalline Definite Molecular structure Inorganic (not from a living thing) Solid material with definite shape Specific physical properties There are over 2,400 minerals that have been identified on Earth! Of these, there are about a dozen of them that are so abundant that they make up more than 90% of the Lithosphere. These very abundant minerals are called the rock formers.
Minerals are made up of elements. Element: A substance composed of atoms which can not be broken down into a more simple substance. Some minerals are made up of only one element but most are made up of two or more elements and are called compounds. Diamond (only 1 element carbon) Halite (compound) *Native Element Minerals: Minerals that occur in nature as single elements. (Ex. Gold, iron, graphite, diamond, sulfur)
ESRT p.16
Chart from cover (p.1) of ESRT Be careful as % by mass and volume aren t the same!
*A Minerals physical properties are determined by its: Internal arrangement of atoms! aka: bonding or atomic structure Internal structure of Halite
Mineral Review II. Physical and Chemical Properties The identification of minerals is done on the basis of well defined physical and chemical properties Physical Properties: Things you can see. Chemical Properties: How a certain substance reacts with other substances. Also includes: Things associated with atomic structure. Carbon Atoms (Graphite and Diamond) Silica Tetrahedron
*A. Color: Unreliable for two reasons: 1. Different minerals are the same color. Ex: Halite and calcite
2. One mineral may have many colors. Only a small impurity can easily change the mineral color. Ex: Calcite or classroom samples of quartz
* B. Streak: The color of a mineral in powder form. We do a streak test using a Streak plate (an unglazed piece of porcelain tile) Note: The color of a mineral may be very different than the streak. Streak is: More reliable than the color. *
Streak (not listed for all minerals)
* C. Hardness: Resistance of a mineral to being scratched. A hard mineral will make a scratch on a softer mineral To compare the hardness of minerals, scientists have developed a scale called the: Moh s scale of hardness. This scale also: compares hardness of common objects (Feldspar) (Iron nail) (Streak plate)
D. Luster: The appearance of light reflected from a mineral s surface. Luster can either be metallic or nonmetallic. a) Metallic: If a mineral shines like a metal. Ex: Galena, Magnetite, and Pyrite b) Nonmetallic: If a mineral does not look like a metal. Ex: Glassy, Waxy, Greasy, Earthy, Dull, etc
Examples of Nonmetallic Luster Earthy Glassy Waxy Dull
E: Cleavage vs. Fracture Cleavage: The tendency of a mineral to break along zones of weakness or flat sides. These zones of weakness appear as smooth planes or surfaces. Fracture: breaking unevenly, no definite cleavage. Beryl (Aquamarine)
Basal Cleavage (One directional) Ex: Mica Remember: If a mineral breaks evenly with cleavage or unevenly with fracture depends on the internal arrangement of its atoms. Cubic Cleavage (three directional at right angles) Ex: Halite Rhombic Cleavage (three directional not at right angles) Ex: Calcite Conchoidal Fracture Ex: Obsidian
* F. Crystal Forms: The geometric shape of a mineral due to its internal arrangement of atoms.
* G. Specific Gravity: The ratio of the density of a mineral compared To the density of water The Density of pure water is 1 g / cc. So, if a mineral had a specific gravity of 3, the density of the mineral would be: 3. g / cc What is going on mathematically? 3 g / cc 1 g / cc Divide density of mineral by density of water = 3 g / cc 1 g / cc Units cancel = 3 Specific gravity of mineral So specific gravity is just like density, but with no units
H) Special Properties of Some Minerals Calcite Reacts with Acid: When HCl is placed on a clean surface, it gives off bubbles of CO 2. Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO 2 gas)
Halite tastes like salt Magnetite exhibits magnetic properties.
Talc feels slippery. Talcum Powder
Fluorescence: Mineral emits visible light when illuminated with high energy light (ultraviolet). Phosphorescence: Mineral emits visible light even after ultraviolet light is switched off. (glows in the dark.)
a) Minerals are crystalline. Crystalline- atoms inside are bonded in a particular pattern or structure Depends on internal arrangement of atoms Two minerals with the same chemical composition but different crystal structure may have very different properties.
Examples: Graphite and Diamond Diamond Both made of pure Carbon Different Bonding Graphite-weak bonds, very soft, used in pencils Diamond-strong bonds, very hard, jewelry/sawblades Graphite
Another Example: Sand and Quartz or Glass Both composed of SiO 2 Different bonding, very different properties Quartz Quartz Sand
b) Minerals may be grouped according to the elements of which they are made, or the compounds which they can form. Examples: Oxides- oxygen with another element Carbonates- metal combined with CO 3 (carbonate formula) Silicates- silicon bonded with oxygen Silicate formula- SiO 4 Silicate building block- tetrahedron Calcium carbonate (limestone) Iron oxide (rust)
Cover of ESRT s The two most abundant elements in Earth s crust by mass and volume are? How many minerals in your ESRT s contain both? minerals Silicate are the most common on Earth!
Igneous Rock Objectives #3. How are igneous rocks formed? (ESRT p.6) #4. Describe how igneous rocks can be classified according to either mineral composition or where they were formed. (ESRT p.6) #5. Explain how igneous rock texture is related to crystal size. (ESRT p.6)
3 Families of Rocks Igneous Sedimentary Metamorphic Let s start first with the mother of all rock families.
Igneous Latin igneus, from ignis fire Of, relating to, or resembling fire. Source: Merriam-Webster
B 1 Igneous Rocks 1. Igneous Rocks: Form from the solidification and/or crystallization of liquid or molten rock : Magma Molten rock underground. : Lava Molten rock above ground. : Solidification The process of becoming a solid igneous rock. Crystallization : Cooling of magma or lava creates crystals. Mineral crystals may form resulting in the igneous rock having a crystalline texture. ***Crystals within a rock are a good indicator of an igneous origin.
II. Igneous Rock Texture and Crystal Size The texture of the igneous rocks (size of the crystals) is dependent upon the rate of cooling. If molten rock cools slowly the crystals will be LARGE. LARGE crystals mean coarse texture ( ). Phaneritic If molten rock cools rapidly the crystals will be small. Small crystals mean fine texture (Aphanitic). Vesicular rocks are created when gases remain trapped in a quickly cooling rock. Air pockets, called vesicles, are the visible evidence. Ex: Scoria When molten rock is quenched (cooled extremely fast), no crystals form and is said to have a glassy texture. Ex: obsidian
Crystal Size Graph showing relative rate of cooling vs. crystal size of igneous rocks Large Small Slow Fast Rate of Cooling
III. Environment of Formation:. Where the rock solidified Intrusive: Plutonic rocks produce Large (1 mm and larger) crystals due to slow underground cooling from magma Extrusive: Volcanic rocks produce Small (less than 1 mm) crystals because lava cools faster near or on Earth s surface
Intrusive igneous rock: Extrusive igneous rock: Deep Underground Near or on Earth s Surface
IV. Composition: The. type of minerals that make up the rock Rocks that are: Felsic : Light in color, low in density,. high in Aluminum Mafic : Dark in color, high in density,. high in iron and magnesium Exception: Obsidian is dark color but felsic composition. Mafic Felsic
Mafic Felsic C. Density:. Depends on the composition of the rock High density Dark in color and Mafic in composition. Low density Light in color and Felsic in composition.
3. Classification of Igneous Rocks Classification based on: A. Color: The. overall color of the rock Light colored rocks are composed primarily of:. Quartz and feldspars Dark colored rocks are composed primarily of:. Pyroxene and Olivine Exception: Obsidian Now let s take a look at your ESRT s
V. Igneous rocks of different composition may form from the same body of magma. some minerals, like quartz and mica melt and solidify at low temperatures and take a long time to solidify out of hot magma. Other minerals such as olivine and pyroxene melt and solidify at higher temperatures. These minerals settle out of magma quicker. This is reason that igneous rocks containing olivine do not usually contain quartz or mica.
Continental Crust vs. Oceanic Crust Continental Crust Oceanic Crust Composition felsic mafic Density low high Color light dark Rock Type granite basalt
Sedimentary Rock Objectives #6. What is a sedimentary rock and what are three good indicators of one? (ESRT p.6) #7. Describe the three types of sedimentary rock and how each is formed. (ESRT p.7)
B 2 Sedimentary Rocks Weathering breaks rock and produces sediments which are transported by water, wind and glaciers. Sediments can form sedimentary rocks in a number of ways. Sedimentary rocks are usually found as a thin coating or veneer on top of other rocks! (like dust on your window sill.) Sedimentary rock often contain rounded particles cemented in layers because running water is the major transporting agent. Many of the rocks form under large bodies of water in 3 major ways.
I. Clastic Sedimentary Rocks: Formed from sediments by the processes of compression (compaction) and cementation Very small compacted clay particles can form shale. Compressionpressure of ocean water and above sediments compact small particles into rock. Microscopic clay-sized fragments
I. Clastic Sedimentary Rocks continued: Cementation- sediments are combined with mineral cements that precipitate out of ground water Precipitate means settle out of solution Three common cements are silica, iron and lime. Common cemented clastic sedimentary rocks are sandstone, breccia and conglomerate.
II. Chemical Sedimentary Rocks (Crystalline, not clastic): Form from processes of evaporation and precipitation Evaporation- salt water evaporates (turns to gas) and leaves solid minerals behind to form rock called evaporites Precipitation- Solid minerals settle to bottom of salt water solution forming rock called precipitates Evaporites and precipitates are monomineralic meaning composed of only one mineral. Four common evaporites and precipitates are rock salt, rock gypsum, dolostone and limestone.
III. Biological or Organic Sedimentary Rocks (Bioclastic) Rocks formed from the remains of plant or animal materials Bituminous Coal comes from compacted plant remains Fossil limestone comes from cemented shells and animal remains
Sedimentary Rocks can be classified into 3 major groups: Clastic Crystalline Bioclastic (Fragmental) (Chemical) (Organic) Origin Underwater In the presence (on the seafloor) of water In the presence of water Composition Fragments of broken rocks Salts (Monominerallic) Once-living remains Method of Lithification (rock formation) Compaction & Cementation Precipitation and evaporation from salty water Compaction of dead material
Sedimentary Rocks are the official rock of Fossils ***If you see a fossil, it s in a sedimentary rock!
Three good indicators of Sedimentary Rocks are: Layers in Rock Presence of sediments Presence of Fossils
Metamorphic Rock Objectives #8: How are metamorphic rocks formed and what are some indicators that metamorphism has taken place? (ESRT p6&7) #9. Explain the two types of metamorphism.
B 3 Metamorphic Rocks Metamorphism usually takes place deep within the Earth. This is where the very high temperatures, high pressures and hot chemical solutions can be found that cause recrystallization forming metamorphic rock.
Metamorphism results in recrystallization of unmelted minerals under high temperatures and pressures. These extreme conditions cause the mineral crystals to grow and new minerals to form without melting which is the process called recrystallization. Larger garnet crystals in schist grow due to intense heat & pressure!
The original rock from which metamorphic rocks are formed is called the. Parent Rock Parent rock may be igneous, sedimentary or metamorphic. Parents Rock! Not a Metamorphic rock
Parent (Shale) They look similar but are different in the following ways Metamorphic Version (Slate)
Indicators of Metamorphism: Metamorphic rocks can be hard, very dense and less porous! Distorted structure: Metamorphic rocks also show bending & twisting due to uneven pressure. Original sedimentary rocks layers may become bent or folded from pressure as they change into metamorphic rock. Garnet and/or mica crystals present helps to identify met. rocks
Metamorphic Rocks are classified into two groups. 1. Foliated: Alignment of minerals or the separation of minerals into platy (flaky) layers of light and. dark bands Foliation commonly appears as Banding. Generally the more intense the temperature and pressure, the thicker the mineral bands will be. Thick banding indicates a high degree of metamorphism.
Notice how your ESRT s shows banding?
2. Non Foliated: Rocks that generally have uniform. Composition (little or no grain arrangement) Non foliated rocks DO NOT have bands Form as a result of equal pressure being applied in all Directions OR contact with hot rock. Pressure equal in all directions Ex: Quartzite and Marble
Two Types of Metamorphism: 1. Contact (Thermal) Metamorphism Occurs where: Molten magma (lava) comes in contact with. other rocks ***The rocks are cooked but not melted.*** Contact metamorphism occurs over a small area. Ex: Vein of magma (dike) or around a magma chamber Vein of magma is hot!!! Contact Metamorphism
Any rock can undergo contact metamorphism as long as the heat is strong enough. Transition Zone - gradual change from original unaltered rock to altered metamorphic
2. Regional Metamorphism Occurs at: Margins of continents where the rock is deeply. buried and exposed to extremely high pressures Ex: Continental Collision and Bottom of Lithosphere Regional metamorphism is associated with orogeny or mountain building processes. Regional metamorphism occurs here over a large area
Name Metamorphic Rock produced from each Parent Rock Shale Slate Sandstone Quartzite Limestone Marble Dolostone Marble Conglomerate Metaconglomerate Granite Gneiss Different metamorphic rocks may be formed from the same parent rock depending upon the pressure and temperature in the environment in which it forms.
Ex: Gneiss, Schist, and Phyllite Depends on Degree of Metamorphism Different metamorphic rocks can be formed from the same parent rock depending on the degree of Metamorphism in which it formed. For example: Shale + H/P Slate + H/P Phyllite + H/P Schist + H/P Gneiss
VI. Distribution of Rock Types a) Covers continent as thin layer or veneer? Sedimentary b) Found at or near surface of volcanoes and mountains? Igneous c) How are intrusive igneous and metamorphic rocks found at Earth s surface instead of deep below? Forces have pushed these rocks upward towards the surface
Rock Cycle Objective #10. Be able to interpret the Rock Cycle diagram on page 6 of the ESRT.
Row, Row, Row Your Rocks Sedimentary rocks, mostly found in layers Often found near water sources with fossils from decayers Then there's igneous rock here since earth was born Molten lava crystallized and that's how they form Metamorphic rocks come from rocks that change Pressure, heat, and chemicals atoms rearrange Rocks changing back and forth a never ending story So many things to know rocks are never boring
C The Rock Cycle The Rock Cycle is: A model to show all possible changes that. rocks can go through. The amount of rock material on Earth remains constant, with the exception of Extraterrestrial material. from space (Meteorite) Any type of rock, Igneous, Sedimentary, or Metamorphic, may be changed into any other type depending upon the environment to which it is subjected. There is no preferred or predictable path that a rock will take within the environment. ESRT Page 6
1. List 3 processes needed for an igneous rock to become sedimentary. 2. What must happen to a sedimentary rock to make it metamorphic? 3. What s one word that all rocks are called before they become igneous rock?
Rock/Mineral Resource Objectives #11. What are fossil fuels and how do they impact our society? #12. Why is the conservation of minerals and resources important?
D. Environment of Rock Formation & Use depend on composition, structure and texture Granite- takes polishing, used for monuments & buildings Gabbro- large dark crystals, used for road base Sandstone- layers, used for building, blocks Slate- easy to cut, used for roofing tiles, flagstone, & pool tables Marble- nonfoliated, used for statues & ornaments
Useful properties of Rocks & Minerals include: Stone for building materials: Roads Buildings Making concrete
Land Use and Rocks What humans can do in a given geographic area often depends on the local bedrock. Limestone rock for farming Granite & gneisses make great bedrock for skyscrapers! (think NYC) Some igneous/metamorphic bedrock forms thins soil and is almost impossible to grow food on. (think Adirondacks Mts.)
Demand for Energy & Resources E. Resource Conservation With the Earth s population rapidly increasing, the demand for energy and resources is rapidly increasing as well. Direct Relationship Earth s Population
At the present time, fossil fuels are primary source of energy. Fossil fuels- Hydrocarbon deposit in Earth formed from organic matter in the past such as coal, oil, and natural gas. Fossil fuels and most minerals are Nonrenewable resources because. they are being used faster than they can form
Coal, oil and natural gas provide most of the worlds energy. These fossil fuels are nonrenewable in our lifetimes. Means we are using them faster than they can be made/replaced What will we do when they become too scarce to obtain??? Fossil Fuels:
Fossil Fuels Beside being used for energy, also used to make plastics, medicines, cosmetics, fabrics, etc.
With such a demand on fossil fuels, some countries have become wealthy due their fossil fuel reserves. Uneven distribution of resources and increasing demand for dwindling resources results in higher prices which alters many peoples standard of living (either for the better or the worse) and in the past has even resulted in wars.
Minerals and Humans: Humans have designed an entire economy around minerals! Without them, our lives would look completely different! Imagine: No electronics (cell phones, TV, video) No gemstones No pencil graphite or lead No cosmetics (sorry girls) No automobiles, bicycles, etc.. The list could go on and on.
Metals for: Electronics Building materials (structural steel) Investment (gold, silver, platinum) Minerals for: Just about everything not plastic! Gemstones (jewelry & investment)
Global Distribution: Minerals can only be mined wherever they are found! Often, mineral resources are found only in remote, hard-to-reach places.
How can we reduce the current usage rate of our natural resources? 1. Practice the 4 R s (Reduce, Reuse, Recycle, Reclaim) 2. Finding and using alternative energy sources (Solar, Hydropower, Wind, Geothermal, and Nuclear Energy) 3. Replace inefficient technology with superior technology