Rocks and Minerals PDF

MINERALS AND ROCKS Minerals and rocks are the significant building blocks of our dynamic Earth. They make up the solid part of the lithosphere and provide us with valuable resources. There are over 5,000 minerals but only a few occur as rock-forming minerals. Rocks are classified according to their...

MINERALS AND ROCKS Minerals and rocks are the significant building blocks of our dynamic Earth. They make up the solid part of the lithosphere and provide us with valuable resources. There are over 5,000 minerals but only a few occur as rock-forming minerals. Rocks are classified according to their origin of the formation. Overtime, rocks are gradually transformed from one type to another in what we call the Rock Cycle. The origin of any rock is determined by careful examination of its texture, composition, and internal structure. This is the basis of rock identification and classification. Minerals Mineralogy is the study of minerals. Minerals are the building blocks of rocks. It is defined as naturally formed, generally inorganic, crystalline solid composed of an ordered array of atoms and having a specific chemical composition. Minerals of the same kind have the same crystal shape. The crystal shape is an external expression of the mineral’s atomic structure. The minerals that make up rocks are called rock- forming minerals. Minerals therefore can be described as: Inorganic-formed by natural geologic process Formed in nature Solids- crystalline substance that are solid at temperature at Earth’s surface Atoms have the same crystalline pattern and with specific chemical composition. Crystalline atoms are arranged in an orderly repetitive manner. Can be represented by a chemical formula Minerals are the fundamental components of rocks. Characteristics of Minerals: composition-represented by a chemical 1. naturally occurring a product of Earth's formula natural processes 5. orderly crystalline structure- atoms of 2. inorganic- it must be a product of Earth's minerals are arranged in an orderly and physical processes. repeating pattern 3. homogeneous solid- minerals should ELS-REVIEWER have definite volume and rigid shape Properties of Minerals: used to identify minerals 1. Color Therese Angeline P. Mifuel GAS 11 A 2. Streak 4. definite chemical 3. Hardness 4. Cleavage 5. Crystalline structure or habit Color 6. Diaphaneity/amount of the mineral's color may change transparency 7. Luster depending on the surface. 8. Tenacity 9. Brittleness Streak 10. Malleability color of mineral in powdered form. 11. Ductility Hardness Luster minerals resistance to scratching. how light is reflected off a surface. Minerals with higher numbers will Categories: Metallic and scratch minerals below. To measure the Non-metallic Metallic-luster of relative hardness of minerals, the Moh's metal scale is used. - shines like a hard metal Many Cleavage non-metallic minerals are SHINY because mineral's resistance to being broken they are transparent or semi-transparent. and fracture. Brittleness - Some minerals split along flat surfaces a mineral turns into powder. (called cleavage planes) when struck hard - this is called mineral cleavage. Malleability a mineral can be flattened by pounding - Other minerals break unevenly with a hammer. (Gold is the most along rough or curved surfaces - this malleable metal) is called fracture. Ductility Diaphaneity/amount of transparency A mineral can be stretched into wire. ability to allow light to pass through it. This is affected by the chemical makeup Flexible but inelastic of the mineral sample. Minerals are bent but they remain in the new position. Chemical Properties of Minerals Flexible and elastic 1.It has a distinctly salty taste. Minerals are bent, and they are 2.Effervesce in hydrochloric acid. brought back to their original 3. Giving off bubbles of carbon dioxide position. Sectility gas. Therese Angeline P. Mifuel GAS 11 ability of minerals to be sliced by a knife A ELS-REVIEWER Moh’s Scale of Hardness One of the most important tests for identifying mineral specimens is the Mohs Hardness Test. This test compares the resistance of a mineral to being scratched by ten reference minerals known as the Mohs Hardness Scale. The test is useful because most specimens of a given mineral are very close to the same hardness. This makes hardness a reliable diagnostic property for most minerals. Friedrich Mohs, a German mineralogist, developed the scale in 1812. He selected ten minerals of distinctly different hardness that ranged from a very soft mineral (talc) to a very hard mineral (diamond). Except for diamonds, the minerals are all relatively common and easy or inexpensive to obtain. Mohs Hardness Scale Mineral Hardness Mineral Hardness Talc 1 Orthoclase 6 Gypsum 2 Quartz 7 Calcite 3 Topaz 8 Fluorite 4 Corundum 9 Apatite 5 Diamond 10 Metallic Minerals Metallic minerals are the minerals that contain one or more metals. In general, they occur as mineral deposits and are a good conductor of heat and electricity, e.g. iron, copper, gold, bauxite, manganese etc. They are malleable and ductile in nature so they can be easily pounded into thin sheets or stretched into wires to make new products. They are generally found in igneous rocks that are formed by cooling and solidification of lava or magma. They are hard and have a shiny surface, so some of them can be used as gems in jewelry. They are also used in various industries for different purposes, e.g. silicon, which is obtained from quartz, is extensively used in the computer industry; aluminum which is obtained from bauxite is used in the automobile and bottling industry. Nonmetallic Minerals Non-metallic minerals are the minerals that do not contain metals, e.g. limestone, mica, coal, gypsum, dolomite, phosphate, salt, manganese, granite etc. They are used in various industries to produce a variety of products, e.g. mica is used in the electrical industry, limestone is used in the cement industry. Furthermore, they are also used in the production of fertilizers and manufacturing of refractories. They are generally found in sedimentary rocks that are formed by the aggregation of various materials like minerals, remains of organisms, rock particles etc. Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER Rocks Rock or stone is a naturally occurring solid aggregate of one or more minerals. The Earth's outer solid layer, the lithosphere, is made of rock. The types and abundance of minerals in a rock are deter-mined by the manner in which the rock was formed. Many rocks contain silica (SiO2); a compound of silicon and oxygen that forms 74.3% of the Earth's crust. This material forms crystals with other compounds in the rock. Rocks can change from one type to another over time more than one mineral not single crystals not usually as pretty no definite shape color is not the same some have fossils How rock type can be changed? Rock can be changed through the processes of weathering, heating, melting, cooling, and compaction. Any one rock type can be changed into a different rock type as its chemical composition and physical characteristics are transformed. The minerals and metals found in rocks have been essential to human civilization. Rocks are classified by: – How they form – Texture – Grain size – Mineral composition Properties of Rocks 1.Rocks exhibit different properties. As to color, rocks may be dark, light, reddish, gray, brown, yellow or even black. 2.Rocks differ in texture: some are fine, others are rough. 3. Some are glossy in appearance and smooth to touch. 4. Most rocks are hard, others are brittle. Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER The rock cycle summarizes the transformational processes that change rocks from one kind to another. It shows the entire journey of rocks formed as they changed. As magma cools and solidifies either deep in the Earth’s crust or at the surface, igneous rocks are formed. When The rocks are exposed, they are subjected to weathering and erosion. The weathered and eroded materials form sediments which are transported and deposited by agents of weathering and erosion such as water and wind. Loose sediments accumulate, compacted, and cemented and formed sedimentary rock in the process called lithification. Sedimentary or igneous rocks may be subjected to further heating and more pressure; thus, they undergo further alteration in the process called metamorphism. The transformed rocks are known as metamorphic rocks. With high temperature alternating with cold temperature, metamorphic rocks are melted producing molten rock or magma. The cycle begins again, and the same processes take place. The rock cycle is an ongoing series of processes inside Earth and on the surface Slowly changes rocks from one kind to another Any type of rock can change into another type How does this relate to plate tectonics? Plate movement drives the rock cycle – Subduction (1 plate pushed under another plate) Re-melts rock into magma – Mountain building Folding, faulting, uplift Exposes rock at the surface to be weathered and erode The Journey of a Rock Mineral-rich water seeps through the sediment and glues, or cements, it together. It becomes a sedimentary rock. Metamorphic Rocks and the Rock Cycle 3 Pressure and heat inside Earth can change it into a metamorphic rock. Metamorphic rock deep inside Earth can melt and begin the cycle again Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER Types of Rocks According to geologists, rocks form in different ways. All rocks can be put into one of those fundamental categories based on their origin. The differences between them have to do with how they are formed. Igneous Rock got its name from a Latin word “ignis” which means fire. The parent material of igneous rock is usually magma, a molten material from deep within the Earth that cools and harden. These rocks are hard and tough. Types of Igneous Rocks Igneous Rocks may be classified into two groups according to where the magma cools and solidifies. A. Intrusive Igneous Rock Some magma rise and flow into the cracks in the crust but do not reach the surface; instead they harden deep inside the crust. They are called igneous intrusive or plutonic igneous. This rock cools slowly and takes thousands or even millions of years to solidify. Most common examples of igneous intrusive rocks. 1. Granite is one of the most important rocks in the crust. It is also the most common rock type. It is a light-colored and coarse grained rock. 2. Gabbro is dark-colored igneous rock often called “ black granite”. The dark color is due to a higher content of iron and the magnesium but with a lower content of quartz. B. Extrusive Igneous Rock Sometimes magma may reach the surface or erupt onto the surface from volcanoes. This extrusion onto the surface is called lava. When lava cools, it solidifies. Since solidification occurs at the surface of the Earth, the rock is called igneous extrusive or volcanic igneous. Most common examples of igneous extrusive. 1. Basalt as a specific rock is usually dark-colored, hard, fine-grained and with high specific gravity. This is due to the high content of iron and magnesium and some feldspar. 2. Obsidian that is formed from lava is also dark-colored but glassy, meaning it has no crystal. During early times, these rocks were used for weapons and tools by shaping them into pointed and sharp-edged objects. 3. Pumice is characterized by the presence of many air holes. This is because gas bubbles are trapped in the rock during the cooling process leaving tiny bubbles. 4. Scoria is formed in the same manner as pumice, but it has larger holes and is much denser and darker. Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER Take note: * Light-colored (high % of silica, less Fe and Mg) igneous rocks are called granitic (gra NIH tihk) rocks. * If the silica content is far less, but it contains more iron, magnesium, or calcium, a dark-colored or basaltic (buh SAWL tihk) rock will result. Intrusive igneous rocks often are granitic, and extrusive igneous rocks often are basaltic. Metamorphic rocks have been changed from heat and high pressure. These rocks got their name from “meta” (change) and “morph” (form). Earth movements can cause rocks to be pressed, bent, or deeply buried under layers of other rocks due to an increase in temperature and pressure. These conditions cause physical and chemical changes in the original rock prolith. The old rocks are forcefully into a new kind in the process known as metamorphism. forms when any rock type is changed into a different kind of rock Changes due to great heat and/or pressure. Marble a hard-crystalline metamorphic form of limestone, typically white with mottling or streaks of color, that can take a polish and is used in sculpture and architecture. Gneiss a metamorphic rock with a banded or foliated structure, typically coarse-grained and consisting mainly of feldspar, quartz, and mica. Quartzite an extremely compact, hard, granular rock consisting essentially of quartz. It often occurs as silicified sandstone, as in sarsen stones. How does rock change? Rocks are heated, squeezed, folded, or chemically changed by contact with hot fluids New rocks that form when existing rocks are heated or squeezed but are not melted are called metamorphic (me tuh MOR fihk) rocks NINE MOST COMMON ROCK-FORMING MINERALS 5. Dolomite 6. Calcite 1. Feldspar 7. Mica 2. Olivine 8. Amphibole 9. Quartz 3. Clay 4. Pyroxene Sedimentary rock When igneous rocks are exposed at the surface, they begin to wear away. They are altered either by physical or chemical weathering processes. Heat from the sun breaks rock apart. Rainwater may fill cracks in rocks and eventually break them down. Sedimentary rocks are formed from lithification, a process of cementing soft, unconsolidated sediments into hard rocks Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER When sediment is dropped, or deposited, by wind, ice, gravity, or water, it collects in layers. After sediment is deposited, it begins the long process of becoming rock. Most sedimentary rocks take thousands to millions of years to form. Sediments are: Rock pieces, Mineral grains, Shell fragments Sedimentary rock can also form from the chemical depositing of materials that were once dissolved in water When water evaporates, minerals are left behind and form rock Sediments form through the processes of weathering and erosion of rocks exposed at Earth’s surface. Three Main Types of Sedimentary Rocks 1.Clastic sedimentary rocks are derived from mechanical weathering which involves the breakdown of rocks into smaller ones at the surface of the crust, accumulate as clasts, piled on top of one another and lithified. 2. Chemical sedimentary rocks form when dissolved materials precipitate. Precipitation is the process of separating a solid substance from liquid. 3. Organic sedimentary rocks are formed by the accumulated sedimentary debris caused by organic processes. These are rocks that may contain fossils of plants and animals trapped in the sediments as the rock was formed.  Conglomerate a rock made up of pebbles, pieces of gravel cemented together. Sandstones are sedimentary rock consisting of sand or quartz grains cemented together, typically red, yellow, or brown in color. Coal a combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground deposits, and widely used as fuel. Exogenic Process Exogenic processes are processes that take place at or near the Earth’s surface that makes the surface wear away. It is very destructive; they are responsible for degradation and sculpting the Earth’s surface. SUMMARY Igneous rocks form from magma or lava. Igneous rocks are classified according to their origin, texture, and composition. Most sedimentary rocks form from sediments that are compacted and cemented together. The three types of sedimentary rocks are clastic rocks, organic rocks, and chemical rocks. In a process that takes place deep beneath the surface, heat and pressure can change any type of rock into metamorphic rock. Geologists classify metamorphic rock according to whether the rock is foliated or nonfoliated. Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER color is usually the same no fossils MINERALS VS ROCKS MINERALS ROCKS Pure (made of same substa more than one mineral not some have crystals single crystals usually pretty not usually as pretty no usually have a shape definite shape color is not the same some have fossils Minerals must be 1. Solid, 2. Inorganic (no living/once living pieces like fossils or shells), 3. Have a specific chemical recipe, 4. Have a crystal (repeating atom pattern) structure, 5. Must be naturally made. Rocks can have organic material, don't have a crystal structure, don't have a specific recipe. Weathering Weathering refers to the changes occurring at or near the surface of the Earth which includes disintegration and decomposition. Disintegration is a mechanical process that breaks large masses of rocks into small fragments while decomposition is a chemical process which results in the formation of new substances such as from elements to rocks. Below is the comparison between mechanical and chemical weathering. TYPES OF WEATHERING MECHANICAL/ PHYSICAL Cause rocks to break into small pieces with each piece retaining the characteristics of the original CHEMICAL Occurs when the internal structure of minerals is changed by the removal or addition of elements. Process that can cause physical weathering Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER Thermal and Pressure Change Rocks crumble and break into fragments because they are subjected to alternating hot and cold temperatures many times. Wind and Waves Wind and Waves can cause all physical weathering. Tiny grains of sand are picked up and carried off by the wind which are then blasted on the surface of rocks, smoothening them. Freeze and Thaw If you put a glass in the freezer it will soon break. This is because water expands when it freezes. Similarly, when water collects in the rock pores and slits, it expands when it freezes. Organic Activity Animals and plants also take a heavy toll on rocks and cause them to wear away. For example, there are animals that dig holes on the ground and exposed rocks. Processes that bring about chemical weathering 1.Hydration/hydrolysis Water is nature’s versatile tool that can bring about chemical weathering. There are other chemical compounds in water that become the main agents of chemical weathering. Molecules of some substance in rocks chemically combine with water molecules. This process is called hydration. 2.Carbonation Carbon dioxide may bond with other substances in a process known as carbonation. Rainwater is naturally acidic because CO2 gas from the atmosphere chemically reacts with it and produces carbonic acid, a weak acid that reacts slowly with carbonate minerals in rocks. 3.Oxidation This is another kind of chemical weathering process. This occurs when oxygen combines with another substance like minerals in rocks yielding compounds called oxides. Erosion Erosion involves the movement of the weathered rock. Loosened rock and mineral debris produced by weathering are eroded and transported to a new location by means of air, wind, water, and gravity. Erosion could result in denudation. The lowering surface of the land mass from which the material was removed is called denudation. Therese Angeline P. Mifuel GAS 11 A ELS-REVIEWER Causes of Erosion 1.Kaingin Method. Trees are cut and burned.Soil losses its fertility. 2. Logging-practice of illegal logging disturbs the soil. 3.Infrastructure projects such as dams, roads, bridges, irrigations and drainage basins, resorts and hydroelectric plant. 4.Mining-companies loosen and dig rocks exposing them to further erosion. 5.Burning grasslands which may lead to accidental fires can destroy plants and leave the soil bare. Effects of Erosion 1.Loss of fertile land 2.Led to increased pollution and sedimentation in streams and rivers Mass Movement (Mass Wasting) Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil, sand, regolith, and rock move downslope typically as a solid, continuous or discontinuous mass, largely under the force of gravity, frequently with characteristics of a flow as in debris flows and mudflows. It is the movement of rock and soil down slope under the influence of gravity. Rock falls, slumps, and debris flows are all examples of mass wasting. Often lubricated by rainfall or agitated by seismic activity, these events may occur very rapidly and move as a flow. Therese Angeline P. Mifuel GAS 11 A