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Rocks and Minerals Ms. Sanderson What is the difference between a Rock and a Mineral? Minerals: – – – – Naturally occurring Inorganic Solid Definite chemical structure (4000 known to man) Rock: made up of minerals (aggregates mixture) Minerals The building blocks of minerals are elements ELEMENTS The Building blocks for minerals. Is a substance that cannot be broken down into simpler substances by chemical or physical means Organized by their properties in the Periodic Table PERIODIC TABLE ELEMENTS ON CRUST OF EARTH Oxygen46.6% Silicon 27.7 % Aluminum 8.1 % Iron 5% Calcium Sodium Potassium Magnesium ATOMS Are the smallest particle of matter that contains the characteristics of an element. Parts of an Atom: Nucleus Central region of the atom. – Contains Protons and Neutrons Energy Levels area where electrons travel Protons Positively charged “+” subatomic particle Found in the nucleus The atomic number of the element Neutrons Neutrally charged subatomic particle Found in the nucleus Same mass as a proton Electrons Smallest part of an atom Negatively charged “—” subatomic particle Found in the energy levels surrounding the nucleus Located in regions called Energy Levels which surround the nucleus ISOTOPES Atoms with the same number of protons but different number of neutrons –Neutron change BONDS Compounds: Is a substance that consists of two or more elements that are chemically combined in specific proportions. Chemical Bond: forces that hold atoms together in a compound Three Types of Bonds – Ionic – Covalent – Metallic Ionic and Covalent Bonds Ionic Atoms gain or lose electrons (transfer of electrons) Between a metal and nonmetal EX: salts, calcium fluoride Covalent Form when atoms share electrons. Between Nonmetal and Nonmetal Ex: Water, diamond METALLIC BONDS Form when electrons are shared by metal ions. Metals are malleable, ductile and conductors. Between Metal and Metal Sharing of electron pool give metals their properties How Minerals Form Four Ways – Crystallization from magma – Precipitation – Changes in Pressure and Temperature – Hydrothermal Solutions Crystallization from Magma As magma cools, elements combine to form minerals. Crystal structure depends on rate of cooling and pressure First to Crystallize: minerals rich in iron, calcium and magnesium Precipitation Water evaporates, some dissolved substances can react to form minerals When minerals are dissolved out of a liquid. Through evaporation or temperature change of water. Examples – Calcite – Halite Pressure and Temperature An increase of pressure can cause a mineral to recrystallize while still solid Changes in temperature can also cause certain minerals to become unstable and recrystallize to form a new mineral that is stable at the new temperature. Examples: talc and muscovite Hydrothermal Solutions Very hot mixture of water and dissolved substance When these solutions come into contact with existing minerals, chemical reactions take place to form new minerals. Examples: – Quartz – Pyrite Mineral Groups Over 3800 minerals have been named Minerals are classified into groups based on their composition – Silicates – Sulfides & Sulfates – Halides – Carbonates – Oxides – Native Elements Silicates Most common group on Earth Silicon and Oxygen combine to form a structure called the silicon-oxygen tetrahedron Two most abundant elements are SILICON AND OXYGEN EX: Quartz Augite Micas Carbonates Second most common mineral group. Contains the element carbon, oxygen and one or more other metallic elements Ex: – Calcite – Dolomite Oxides Minerals that contain oxygen and one or more other elements, which are usually metals Ex: – Rutile – Corundum – Hematite Sulfides & Sulfates Contains the element sulfur & other elements Ex: – Gypsum – Galena – Pyrite Halides Contains a halogen ion plus one or more other elements. Elements from Group 7A on the periodic table-like fluorine and chlorine. Ex: – Halite – Fluorite Native Elements Group of minerals that exist in relatively pure form Ex: – Gold – Silver – Copper – Sulfur – Carbon Properties of Minerals—used to identify minerals Streak Color Luster Crystal Form Hardness Scale Cleavage Fracture Density Texture Magnetic Conductor Reaction with Acid Color Not a useful tool for identification Small amount of different elements can give the same mineral different colors Olivine = greenish tint Streak The color of a mineral in its powdered form. Found by rubbing mineral across a streak plate. Example: Galena (below) using an unglazed porcelain tile Luster How light is reflected from the surface of a mineral (how shiny it is) Two types: Metallic: looks like a metal & Nonmetallic: does not look like a metal Crystal Form Visible expression of minerals internal arrangement of atoms Structure of the minerals Size depends on the length exposed to heat Hardness A measure of the resistance of a mineral to being scratched Measured on Mohs Hardness scale 10 minerals arranged from 10 (hardest) to 1 (softest) Finger Nail2.5 Copper penny 3.5 Glass 5.5 Streak Plate 6.5 Cleavage Tendency of a mineral to break along flat even planes. Micas show the simplest type of cleavage. Fracture The uneven breakage of a mineral If a mineral does not have cleavage then it has fracture Density The ratio of an objects mass to its volume. Each mineral has its own unique density Density of Gold is 19.3 g/cm^3 Other: Texture (soapy, greasy) Magnetism (attraction to a magnet) Smell (sulfur smells like a rotten egg) Reaction to acid (mineral fizzes) Double Refractions – When a piece of transparent calcite is placed over printed material, the letters appear doubled. Texture What does it feels like. Mica - brittle Talc - soapy Magnetic Attracted or repelled by a magnet. Example: Magnetite Conductor Does it conduct electricity? Rxn with Acid Does it fizz in acid? Mostly tested with HCL. Calcite below: What is a ROCK? Any solid mass of mineral or minerallike matter that occurs naturally as part of our planet Three types of rock: 1. 2. 3. Igneous Sedimentary Metamorphic The Rock Cycle Interaction among Earths water, air, land, and living things can cause rocks to change from one type to another A continuous process Igneous Rocks Form when magma or lava hardens LAVA vs. MAGMA Lava Molten rock on the surface of Earth Magma Molten rock beneath Earth’s surface Formation of Igneous Rocks Intrusive Igneous Rocks Rocks that form when magma hardens beneath Earth’s surface EX: Granite Extrusive Igneous Rocks Rocks that form when lava hardens on the surface of the Earth EX: Rhyolite Classification of Igneous Rocks Texture & composition are two characteristics used to classify igneous rocks. Classification of Igneous Rocks Texture=size, shape, and arrangement of interlocking crystals OBSIDIAN-EXTRUSIVE Texture Coarse-Grained Slow cooling Large crystals Fine-Grained Rapid cooling of magma or lava Small, interconnected mineral grains Peridotite Intrustive Andesite--extrusive Texture Glassy Extrusive Igneous Rock Looks like glass Obsidian--extrusive Porphyritic Large crystals embedded in a matrix of much smaller crystals Porphyritic Andesiteextrusive Composition Composition=Based on proportions of light and dark minerals Types – Granitic – Basaltic – Andesitic – Ultramafic Composition Basaltic Contains many dark silicate minerals and plagioclase feldspar Rich in magnesium & iron Example: basalt & gabbro Composition Granitic Made almost entirely of light-colored silicate minerals like quartz and feldspar 0 to 25% dark minerals Example: biotite & amphibole Other Composition Andesitic Between granitic and basaltic At least 25% dark minerals Composition Ultramafic Composed mainly of iron and magnesium-rich minerals Almost entirely dark minerals Comp/ Texture Granite Andesitic Basaltic Ultramafic Coarse Granite Fine Phyolite Andesite Diorite Gabbro Periodtite Basalt Kematite Porphyritic Inside any given rock Glassy Obsidian, Pumice Uncommon What is a Sedimentary Rock? Forms when existing rocks are broken down into sediment then compacted and cemented together Formation of Sedimentary Rock Involves – Weathering is the next step—any process that breaks rocks into sediment. – Erosion– the removal of weathered rocks Formation of Sedimentary Rocks – Deposition-- When the agents of erosion (wind, water, ice or gravity) loses energy, it drops the sediment. – Compaction—process that squeezes or compacts sediment together – Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediment Classification of Sedimentary Rock Classified into two main groups according to the way they form. – Either Clastic or Chemical Rock Salt Chemical Clastic Sedimentary Rock Made of weathered bits of rocks & minerals Grouped according to size of the sediments Conglomerate Clastic Grain size Sediment Name Rock Name Coarse (over 2mm in size) Gravel-rounded Conglomerate Gravel-angular Breccia Medium (2mm to 1/6 mm) Sand Sandstone Fine (1/16 to 1/256 mm) Silt Siltstone Very fine (less than 1/256 mm) Mud Shale/mudstone Chemical Sedimentary Rock Form when dissolved minerals precipitate from water solution (Rock salt and flint) Biochemical Sedimentary Rocks – Made from once living organisms like shells and skeleton remains – Ex: Chalk, Limestone, rock salt Composition Texture Rock Name Calcite Limestone Coquina Chalk Quartz Fine to coarse Visible shells Small shells and clay Very fine Gypsum Fine to coarse Rock Gypsum Halite Fine to coarse Rock Salt Altered plant fragments Fine-grained organic matter Coal Chert (light colored) Flint (dark colored) What is a Metamorphic Rock Form when existing rocks are changed by heat and pressure Metamorphism— means “change form” Agents of Metamorphism The agents of metamorphism are –Heat provides the energy needed to drive chemical reactions which causes existing minerals to recrystallize. Agents of Metamorphism –Pressure applied in all directions on a rock which causes spaces between grains to close –Hydrothermal solutions hot, water solution that promote recrystallization by dissolving original minerals & then depositing new ones Classification of Metamorphic Rocks Classified by texture & composition – Texture Foliated Non-foliated – Composition Greenstone Non-foliated Foliated Metamorphic Rocks A rock with layered or banded appearance that had been metamorphosed Example: Gneiss Four Main Types – – – – Slate Phyllite Schist Gneiss Gneiss Slate Phyllite Schist Gneiss Non-foliated Metamorphic Rocks Does not have a banded texture Contains only one mineral Ex: Marble – Calcite crystals Quartzite—made from Quartz Anthracite—made of Coal Rock Name Slate foliated Grain Size Very fine Phyllite foliated Fine Schist foliated Medium to coarse Phyllite Gneiss foliated Medium to coarse Schist, phyllite, or volcanic rocks Marble Nonfoliated Nonfoliated Medium to coarse Limestone, dolostone Medium to coarse Quartz sandstone Quartzite Texture Parent Rock Shale, mudstone, or siltstone Slate
