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

MOST COMMON ELEMENTS ON CRUST OF EARTH  Oxygen  46.6%  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 Augite Micas 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 Nail  2.5  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.

TextureMagnetic  What does it feels like.  Mica - brittle  Talc - soapy  Attracted or repelled by a magnet.  Example: Magnetite

ConductorRxn with Acid  Does it conduct electricity?  Does it fizz in acid?  Mostly tested with HCL. Calcite below:

What is a ROCK?  Any solid mass of mineral or mineral- like matter that occurs naturally as part of our planet

Three types of rock: 1. Igneous 2. Sedimentary 3. 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 Porphyritic  Large crystals embedded in a matrix of much smaller crystals Porphyritic Andesite- extrusive Obsidian--extrusive

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/TextureGraniteAndesiticBasalticUltramafic CoarseGraniteDioriteGabbroPeriodtite FinePhyoliteAndesiteBasaltKematite Porphyritic Inside any given rock Uncommon Glassy Obsidian, Pumice

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-roundedConglomerate Gravel-angularBreccia Medium (2mm to 1/6 mm) SandSandstone Fine (1/16 to 1/256 mm) SiltSiltstone Very fine (less than 1/256 mm) MudShale/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

CompositionTexture Rock Name Calcite Fine to coarse Visible shells Small shells and clay LimestoneCoquinaChalk Quartz Very fine Chert (light colored) Flint (dark colored) Gypsum Fine to coarse Rock Gypsum Halite Fine to coarse Rock Salt Altered plant fragments Fine-grained organic matter Coal

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 Texture Grain Size Parent Rock Slatefoliated Very fine Shale, mudstone, or siltstone PhyllitefoliatedFineSlate Schistfoliated Medium to coarse Phyllite Gneissfoliated Schist, phyllite, or volcanic rocks Marble Non- foliated Medium to coarse Limestone, dolostone Quartzite Non- foliated Medium to coarse Quartz sandstone Anthracite Non- foliated fineCoal