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THE EARTH THROUGH TIME TENTH EDITION H A R O L D L. L E V I N © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 1 CHAPTER 4 Rocks and Minerals: Documents that Record Earth's History © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 2 WHAT CAN MINERALS TELL US? Minerals form under specific set of physical conditions (pressure, temperature, and composition). Thus the presents or absents of a mineral informs on the conditions under which they form. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 3 WHAT CAN MINERALS TELL US? 1. Radiometric age dating - Minerals containing radioactive elements. 2. Igneous Rocks - Minerals that crystallize from magmas and lavas provide information about temperature, viscosity, composition, type of volcano, and tectonic setting. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 4 WHAT CAN MINERALS TELL US? 3. Metamorphic rocks: Minerals can provide information about temperature, pressure, and composition (both mineral & fluids). From this information which we can determine the depth at which metamorphism occurred, parent rock, and information about the history of the formation of mountain ranges. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 5 WHAT CAN MINERALS TELL US? 4. Sedimentary Rocks: Minerals that form by evaporation in arid climates can tell us about paleoclimatic conditions. Since some climates are controlled by latitude, we can make general inferences about latitude. 5. Sedimentary Rocks: Minerals that form in sea water tell us about the nature of ancient seas and the organisms that lived in them. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 6 WHAT CAN MINERALS TELL US? 6. Sedimentary Rocks: Minerals can provide information on the tectonic setting, amount of relief, paleoclimate, and types of rocks that are eroding in the source area. 7. Sedimentary Rocks: Minerals can also tell us about the changing chemistry of the atmosphere, for example, the presence or absence of oxygen. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 7 WHAT CAN MINERALS TELL US? 8. Igneous/Sedimentary Rocks: Minerals containing iron can record the orientation of the Earth's magnetic field, which yields information on latitude, and provides evidence for drifting continents, sea floor spreading, and movement and reversal of the Earth's magnetic poles. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 8 MINERALS By definition, minerals are: 1. 2. 3. 4. 5. Naturally occurring Inorganic Solid Definite chemical composition Orderly internal crystal structure © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 9 MINERALS EACH MINERAL HAS UNIQUE SET OF PHYSICAL AND CHEMICAL PROPERTIES, WHICH ALLOW FOR THE IDENTIFICATION OF THE DIFFERENT SPECIES OF MINERALS. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 10 SOME PHYSICAL PROPERTIES OF MINERALS color streak luster hardness density crystal form cleavage © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. fracture magnetism reaction to acid taste flexibility feel 11 PHYSICAL PROPERTIES OF MINERALS Color - the color or range of colors of a mineral as it appears to the eye in reflected light. Examples: Quartz may be colorless, white, pink, purple, dark brown, green or blue. Malachite is always green. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 12 PHYSICAL PROPERTIES OF MINERALS Luster - the character of the light reflected off of a mineral surface. A mineral may have a metallic luster (looks like polished metal) or a non-metallic luster. Luster is independent of color. Example: Galena has a metallic luster Quartz has a non-metallic luster © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 13 PHYSICAL PROPERTIES OF MINERALS Streak - the color of a mineral when it is ground to a powder against white unglazed porcelain. Streak color may be quite different from the whole mineral color and is particularly useful for identifying metallic luster minerals Examples: Hematite may be silver or gray, but it has a reddish brown streak. Pyrite is gold, but is has a black streak. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 14 PHYSICAL PROPERTIES OF MINERALS Hardness - the resistance of a mineral to scratching. Mohs Hardness Scale is a relative scale from 1 - 10 based on a series of minerals. Talk is the softest and diamond is the hardest. Hardness of minerals can also be compared to common objects (fingernail, copper penny, nail, glass). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Talc (softest) Gypsum← fingernail Calcite← penny (copper) Fluorite← nail Apatite← glass Orthoclase Quartz Topaz Corundum Diamond (hardest) 15 PHYSICAL PROPERTIES OF MINERALS Density - How heavy a mineral is for its size. Density is the ratio of the mass of an object divided by its volume. D = Mass/Volume Examples: Quartz has a density of 2.65 g/cm3. Gold has a density of 19.3 g/cm3. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 16 PHYSICAL PROPERTIES OF MINERALS Crystal form - some minerals are in the form of crystals. Crystal shape is related to the structural arrangement of atoms within the mineral. Perfect crystals are rare because minerals typically grow close together in confined spaces, producing a mass of interlocking crystals. A crystal which form in a large space may develop perfect crystal faces. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 17 PHYSICAL PROPERTIES OF MINERALS Cleavage - the tendency of a mineral to break along flat surfaces related to planes of weakness in its crystal structure. Minerals can be identified by the number of cleavage planes they exhibit, and the angles between them. Examples: Some minerals tend to cleave or break into flat sheets (the micas: muscovite and biotite). Others break into cubes (halite), or into rhombs (calcite and dolomite). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 18 PHYSICAL PROPERTIES OF MINERALS Fracture - irregular breakage, not related to planes of weakness in the mineral. Some minerals, such as quartz and olivine, do not have cleavage. They have a type of fracture called conchoidal fracture. Conchoidal fracture produces curved breakage surfaces, as seen on arrowheads or chipped glass. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 19 PHYSICAL PROPERTIES OF MINERALS Magnetism - A few minerals are magnetic. They are attracted to a magnet, or they act as a natural magnet, attracting small steel objects such as paperclips. Reaction to acid - The carbonate minerals react with diluted hydrochloric acid (HCl) by effervescing or fizzing, producing bubbles of carbon dioxide gas. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 20 PHYSICAL PROPERTIES OF MINERALS Taste - Some minerals have a distinctive taste. Halite (or table salt) has a salty taste. Flexibility - Some minerals can be bent easily such as biotite mica. Feel - Some minerals have a distinctive feel to the fingers such as talk which feels soapy. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 21 ROCK-FORMING MINERALS There are more than 3000 minerals on the Earth, but only a few are common and make up most of the rocks. The common rock-forming minerals can be divided into two groups: Silicates (most common) Non-silicates. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 22 SILICATE MINERALS Earth's crust is dominated by 8 elements from the periodic chart. Of these 2 elements make up the majority: Oxygen (46.6% by weight) Silicon (27.7% by weight) These two elements combine to form a structure know as the silicate tetrahedron (pyramid shape) that is used as a building block to construct the rock forming silicate minerals Examples: quartz, feldspar, mica © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 23 SILICATE MINERALS—FELDSPAR GROUP Dominant mineral in Earth's crust. Two directions of cleavage at 90o Flat, glassy rectangular surfaces. Color may be white, pink, gray, green. Common in igneous rocks such as granite and basalt. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Harold Levin 24 SILICATE MINERALS - FELDSPAR GROUP Two major types: Orthoclase (potassium feldspar) - KAlSi3O8 Plagioclase - A range of compositions with sodium and calcium. Calcium-rich = anorthite (CaAl2Si2O8) Sodium-rich = albite (NaAlSi3O8) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 25 SILICATE MINERALS - QUARTZ Second-most abundant mineral in Earth's crust. Color varies colorless, white (milky quartz), gray to brown (smoky quartz), pink (rose quartz), purple (amethyst), blue, or green. Hard (scratches glass) Glassy luster Conchoidal fracture Six-sided, elongated crystals © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 26 SILICATE MINERALS - QUARTZ Common in silica rich igneous rocks such as granite. Quartz is found in sedimentary rocks both as a resistant weathering byproduct (quartz sandstone) and as a chemical precipitate (chert). A common metamorphic rock dominated by quartz is quartzite. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 27 SILICATE MINERALS - MICA Perfect cleavage in one direction causing it to split into thin sheets. Two types: Muscovite - Colorless or silver-colored mica. Biotite - Black or dark brown mica (contains Mg and Fe). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 28 SILICATE MINERALS - AMPHIBOLES Two directions of cleavage, not at 90o Narrow, elongated crystals Typically dark in color (black or dark green). Common in metamorphic rock amphibolite. Example: Hornblende. Contains Mg and Fe. Harold Levin © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 29 SILICATE MINERALS - OLIVINE Olive green color Glassy texture. No cleavage. Conchoidal fracture. Contains Mg and Fe. Main constituent of the ultramafic rock, peridotite (birthstone = peridot). Mark A. Schneider/Photo Researchers, Inc. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 30 SILICATE MINERALS - CLAYS Group of minerals formed from weathering of feldspars and some other minerals. Very fine-grained Dull, earthy luster Soft, smooth feel Example: Kaolinite, a white clay with many economic uses. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 31 NON-SILICATE MINERALS Non-silicate minerals comprise about 8% of the Earth's crust. Carbonate minerals are the most widespread and are based on the anion CO3-2. Types: native elements oxides sulfides sulfates © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. carbonates halides phosphates, etc. 32 CARBONATE MINERALS Calcium carbonate. Calcite (CaCO3) & Aragonite (CaCO3) Calcium magnesium carbonate. Dolomite (CaMg(CO3)2) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 33 CALCITE Main constituent of limestone and marble. Typically the Shell remains of some marine organisms. Fizzes in hydrochloric acid. Has rhombohedral cleavage (three directions not at 90o). Cleavage fragments are rhombs. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 34 ARAGONITE Same chemical formula as calcite, but it has a different crystal structure. Shells and skeletons of corals and mollusks (clams and snails). Fizzes in hydrochloric acid. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 35 DOLOMITE Has rhombohedral cleavage like calcite. Will fizz in acid only when scratched or powdered. Main constituent of sedimentary rock dolostone or dolomite. Forms from alteration of limestone through the addition of Mg. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 36 EVAPORITE MINERALS Halite (NaCl) Gypsum (CaSO4 . 2H2O) Anhydrite (CaSO4) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 37 HALITE Major constituent of rock salt (and table salt). Typically colorless to white. Cubic cleavage Salty taste. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 38 GYPSUM Major constituent of rock gypsum. Soft - can be scratched by fingernail. Typically white or colorless to pink. Varieties: Selenite - clear crystals with rhombohedral cleavage Alabaster - fine-grained and massive Satin spar - fibrous © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 39 ANHYDRITE Like gypsum, but without the water. (anhydrous = without water.) Forms from the de-watering of gypsum. A relatively common sedimentary mineral. May be white, gray, colorless or blue. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 40 ROCKS A rock is a solid aggregate of one or more minerals, rock fragments, and/or organic matter. Rocks are the building blocks of the Earth's crust. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 41 ROCKS 1. Igneous - Crystallized from hot, molten state. Examples: granite & basalt 2. Sedimentary – The hardening of sediment derived from weathering by compression or cementation at or near the Earth’s surface. Examples: sandstone, shale, & limestone 3. Metamorphic - Rocks changed by heat and/or pressure or chemical activity while in the solid state with in the Earth’s crust. Examples: gneiss, schist, slate, & marble © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 42 THE ROCK CYCLE Through the rock cycle, one type of rock can be converted into another. FIGURE 4-18 The rock cycle. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 43 IGNEOUS ROCKS The word igneous means "fire-formed.“ Magma - molten rock beneath the Earth’s surface. Lava - molten rock that has flowed out on the Earth’s surface. Extrusive or volcanic rocks form from lava, which cooled on the Earth's surface. Examples: Basalt, rhyolite, andesite, obsidian Intrusive or plutonic igneous rocks form from magma which cooled beneath the surface of the Earth. Examples: Granite, gabbro, diorite © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 44 COOLING HISTORY AND GRAIN SIZE The texture of a rock is a description of its grain size, shape, and arrangement. Cooling rates influence the texture of igneous rocks. Volcanic rocks cool quickly Plutonic rocks cool slowly due to the insulating quality of the crust. Volcanic rocks quick cooling fine grained Plutonic rocks slow cooling coarse grained © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 45 EXTRUSIVE VS. INTRUSIVE Harold Levin Granite - coarse-grained, intrusive igneous rock. Harold Levin Rhyolite - fine-grained, extrusive igneous rock. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 46 IGNEOUS ROCK CLASSIFICATION Igneous rocks are classified on the basis of: Texture (or grain size) Composition – Based on the amount of silica present Light Colored 1. 2. 3. Dark Colored 4. Sialic - Silica-rich Intermediate Mafic - Silica-poor Ultra Mafic – Very Silica poor © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 47 IGNEOUS ROCK CLASSIFICATION FIGURE 4-25 Mineral composition, texture, and other properties for common igneous rocks. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 48 BOWEN'S REACTION SERIES Minerals in igneous rocks crystallize in a particular order, at particular temperatures. FIGURE 4-27 Bowen’s Reaction Series. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 49 SEDIMENTARY ROCKS Cover about 75% of the world's land area. Sediment is deposited originally in horizontal layers. A major characteristic of sedimentary rock is layering, also called bedding or strata. Sedimentary rocks contain the fossil record, which preserves the evolving story of life on Earth. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 50 WHAT CAN SEDIMENTARY ROCKS TELL US? Locations of ancient sedimentary environments (seas, reefs, deltas, beaches, rivers, lakes deserts, glaciers, and mountains). Ancient climates humid tropical coal swamps, dry windswept deserts, glacial ice sheets, high temperatures and high sea levels. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 51 HOW IS SEDIMENT FORMED? Sediment forms from the weathering and erosion of rocks, as part of the rock cycle at or near the Earth’s surface. Two categories of weathering: Mechanical (physical) – Processes that break down a rock into smaller versions of its self. Chemical – Processes that alters the chemical makeup of a rock to from new minerals and dissolved ions. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 52 WEATHERING OF GRANITE IN A HUMID CLIMATE 1. 2. 3. 4. 5. Feldspars undergo hydrolysis to form clay. Biotite and amphibole undergo hydrolysis to form clay, and oxidation to form iron oxides. Na, Ca, and K ions are lost in solution and washed away. Small amounts of Si from feldspars, biotite, and amphibole are lost in solution. Quartz remains as sand grains due to its resistance to weathering. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 53 FATE OF THE WEATHERING PRODUCTS Clay minerals form shale Iron oxides form cement, ochre, or iron ore Dissolved Na, Ca, and K ions form limestone, evaporites, or become included in shale Dissolved Si ions form chert, silica cement, or diatomite Unaltered quartz grains form sandstone © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 54 EXAMPLE: GRANITE WEATHERING IN A HUMID CLIMATE © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 55 TYPES OF SEDIMENTARY ROCKS Clastic Sedimentary Rocks (also called detrital or terrigenous) Chemical / biochemical Sedimentary Rocks Organic Sedimentary Rocks (Coal) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 56 CLASTIC SEDIMENTARY ROCKS Clastic sedimentary rocks are derived from the mechanical weathering of pre-existing rocks, which have been transported to the depositional basin. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 57 CLASTIC TEXTURE Clasts (larger pieces or fragments) Matrix (mud or fine-grained sediment surrounding the clasts) Cement (the chemical "glue" that holds it all together) Types of cement: Calcite Iron oxide Silica © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 58 CLASTIC SEDIMENTARY ROCKS ARE CLASSIFIED BY GRAIN SIZE Gravel - Grain size greater than 2 mm Sand - Grain size 1/16 to 2 mm Silt - Grain size 1/256 to 1/16 mm Clay - Grain size less than 1/256 mm © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 59 CLASTIC SEDIMENTARY ROCKS ARE CLASSIFIED BY GRAIN SIZE Grain size Rock name Gravel Conglomerate = rounded clasts Breccia = angular clasts Sand Sandstone Silt Siltstone Clay Shale = fissile Claystone = massive © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 60 CHEMICAL/BIOCHEMICAL SEDIMENTARY ROCKS 1. 2. 3. Evaporites - form from the evaporation of water Carbonate rocks - form by chemical processes and biochemical processes Siliceous rocks - form from chemical processes (silica replacing limestone) or biochemical processes (silica-secreting organisms) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 61 EVAPORITES 1. 2. 3. Rock salt - composed of halite (NaCl). Rock gypsum - composed of gypsum (CaSO4 . 2H2O) Travertine - composed of calcium carbonate (CaCO3) – a carbonate rock; forms in caves and around hot springs. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 62 CARBONATE ROCKS 1. Limestones 2. Micrite (microcrystalline limestone) Oolitic limestone Fossiliferous limestone Coquina Chalk Crystalline limestone Others Dolostones or dolomites © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 63 SILICEOUS ROCKS Diatomite - made of microscopic plankton called diatoms. Look like miniature petri dishes Chert - massive and hard, microcrystalline quartz. May be dark or light in color. Often replaces limestone or are skeletal parts. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 64 ORGANIC SEDIMENTARY ROCKS - COAL Composed of organic matter (plant fragments). With increasing depth of burial (temperature and pressure): Peat Lignite Bituminous coal Anthracite coal © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 65 METAMORPHIC ROCKS Metamorphic means "changed form." Metamorphism causes changes in the texture and mineralogy of rocks. Rocks are changed or metamorphosed by: 1. 2. 3. High temperatures High pressures Chemical reactions caused by solutions and hot gases © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 66 METAMORPHIC INDEX MINERALS Certain minerals form during metamorphism, under specific pressure and temperature conditions. These minerals can be used as a guide to metamorphic pressures and temperatures. They are called metamorphic index minerals. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 67 METAMORPHIC INDEX MINERALS Chlorite and muscovite form at relatively low temperatures. Biotite and garnet form at somewhat higher temperatures and pressures. Staurolite and kyanite form at intermediate to high temperatures and pressures. Sillimanite forms at the highest temperatures and pressures. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 68 METAMORPHIC INDEX MINERALS From studies of minerals in metamorphic rocks it is possible to determine the conditions under which the rocks formed. FIGURE 4-41 How shale progressively metamorphoses to other rock types in response to increasing temperature and pressure. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 69 TYPES OF METAMORPHISM 1. 2. Contact metamorphism Alteration of rock by heat and chemically active fluids adjacent to hot molten lava or magma. Pressure is less of an influence. Regional metamorphism Alteration of rock over a large area by heat and pressure due to deep burial or tectonic processes. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 70 TYPES OF METAMORPHIC ROCKS Metamorphic rocks are separated into two groups on the basis of texture. • Foliated • Non-foliated (or granular) Foliation = Laminated structure in a metamorphic rock resulting from the parallel alignment of minerals (usually micas) preferred growth directions. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 71 FOLIATED METAMORPHIC ROCKS In order of increasing grade of metamorphism: Slate Low Grade (Low Temp. & Press.) Phyllite Schist High Grade (High Temp. & Press.) Gneiss © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 72 FOLIATED METAMORPHIC ROCKS Slate - Mica flakes are microscopic in size (clay size). Derived from the regional metamorphism of shale. Slits into flat planes. Phyllite - Mica flakes increase in size over slate, but are still microscopic. Other minerals such as garnet or staurolite may also be present. Derived from the regional metamorphism of shale. Tends to have a wavy appearance. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 73 Harold Levin Robert D. Tucker FOLIATED METAMORPHIC ROCKS Schist - Mica flakes are visible to the unaided eye. Derived from the regional metamorphism of shales or fine-grained volcanic rocks. Gneiss - Coarse-grained rock with minerals segregated into light and dark layers or bands. Derived from the regional metamorphism of high-silica igneous rocks, and muddy sandstones. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 74 NON-FOLIATED METAMORPHIC ROCKS Non-foliated or granular metamorphic rocks are composed of equidimensional grains such as quartz or calcite. There is no preferred orientation. The grains form a mosaic. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 75 Quartzite - Composed of finelyto coarsely-crystalline quartz. Derived from the metamorphism of quartz sandstone. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. Harold Levin Marble - Composed of finely- to coarsely-crystalline calcite or dolomite. Derived from the metamorphism of limestone or dolostone. Commonly white or gray. May be pink. Andrew J. Martinez/Photo Researchers, Inc. NON-FOLIATED METAMORPHIC ROCKS 76 NON-FOLIATED METAMORPHIC ROCKS Greenstone - Contains iron- and magnesium-rich green minerals such as chlorite and epidote. Finegrained texture. Derived from the low-grade metamorphism of basalt. Hornfels - Very hard, fine-grained rock. Derived from the contact metamorphism of shale and other finegrained rocks. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 77 RECAP: THE ROCK CYCLE FIGURE 4-18 The rock cycle. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 78 IMAGE CREDITS • FIGURE 4-18 The rock cycle. Source: Harold Levin. • FIGURE 4-25 Mineral composition, texture, and other properties for common igneous rocks. Source: Harold Levin. • FIGURE 4-27 Bowen’s Reaction Series. Source: Harold Levin. • FIGURE 4-41 How shale progressively metamorphoses to other rock types in response to increasing temperature and pressure. Source: Harold Levin. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED. 79