Geo 101 1st Edition Lecture 4Outline of Last Lecture 1. Theory of Plate Tectonics2. Continental Drift 3. Wegner’s Hypothesis4. Continental Drift, Renewed Interest5. Earth’s Magnetic Field 6. Continental Drift &Paleomagetism7. A Scientific Revolution Begins a. Seafloor Mapping 8. Plate Tectonics: The New Paradigm Outline of Current Lecture 1. Minerals: Building blocks of rocks 2. What is a mineral? 3. Composition of Minerals 4. Chemistry Refresher a. Structure of Atom b. Chemical Bonding i. Ionic ii. Covalent iii. Metallic iv. Van Der Walls 5. Structure of Minerals 6. How do we Identify Minerals a. Diagnostic Properties i. Crystal Form/Shapeii. Lusteriii. Coloriv. Streakv. Harnessvi. Cleavage vii. Fractureviii. Specific Gravity ix. Other Properties 7. Mineral groups8. Categories of Silicate Minerals9. Non-Silicate Minerals These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Current LecturePatterns in Nature: Minerals Minerals: Building blocks of rocks - Minerals are NOT rocks!- Rocks are made up of minerals What is a mineral? - By definition a mineral is: o Naturally occurring o Homogeneouso Define chemical composition o Inorganic crystalline solid  Minerals have an ordered, internal arrangement of atoms Composition of Minerals - Elementso Building blocks of minerals (i.e. minerals – one or more elements)o Over 100 different elements - Atoms o Smallest particles of matter o Building blocks of elements Chemistry Refresher- Structure of Atom o Nucleus  Protons (+) Neutrons (no charge)o Electrons (-) Surround nucleus  Located in energy levels called shells; each shell generally has room to hold 8 electrons  Shells are most stable when they are filled What defines an element?- An element is chemically defined by the number of protons o Different number of neutrons: isotope (ex: C-14 and C-12)o Different number of electrons: ion  Cation: positive charge  Anion: negative charge Chemical Bonding - Combining 2 or more elements to form a compound (e.g. minerals) - 1. Ionic bonding o Atoms gain or lose outermost electrons, creating ions o Ionic compounds have an orderly arrangement of oppositely charged ions (“opposites attract”)o Makes them electronically stable or neutral - 2. Covalent Bonding o Atoms share electrons to achieve electrical neutrality (try to fill their outer electron shells) o Stronger Ionic Bond - 3. Metallic bonds o Electrons migrate among atoms; good conductivity  Ex: copper & gold  Makes really good conductors  Most things are metals - 4. Van Der Waals Bonds o Weak attractive force between electrically-neutral atoms: stacking interaction  Ex: graphite REVIEW QUESTIONS:Which of the following is NOT a characteristic defining a mineral?- Random internal structure What type of bonding occurs when atoms share electrons? - Covalent Which type of chemical bond is the weakest? - Van Der WaalsStructure of Minerals - Minerals: orderly array of atoms, bonded to form a crystalline structure - Different atoms will pack into different arrangements o Tetrahedron o Octahedron o Cubeo Cuboctahedron o ETC. - Orderly arrangement givens minerals symmetry - Polymorphis o Minerals with the same composition but different crystalline structures  Ex: diamond and graphite are polymorphis of carbon How do we identify minerals? - Primary Diagnostic properties o Determined by observation or performing simple testso Several physical properties are used to identify hand samples of minerals Diagnostic properties - Crystal Form/Shape o External expression of mineral’s internal structure (i.e. how atoms are arranged) - Luster o Appearance in reflected light o 2 major categories  Metallic (looks like metal)  Nonmetallic - Color o Generally unreliable for mineral ID; variable due to impurities in mineral chemistry o Colorations of minerals produce gemstone o Most unreliable o Corundum  Blue – sapphire (if you mix iron)  Red – rubies (if you mix chromium)  So sapphires and rubies are the same thing but mixed with something else o Beryl  Green – emeralds (chromium) Blue – aquamarine (iron)  Again, same thing - Streak o Color of a mineral in its powdered form o Obtained by scratching the mineral on a porcelain plate o Can be different from color because in powder form, the effect of impurities is reduced- Hardness o Resistance of a mineral to abrasion or scratching o All minerals are compared to a standard scale called the Mohs hardness scale Goes from 1-10 Low number is softer Diamond is a 10  Tale is a 1  Measuring hardness of minerals against other minerals - Cleavage o Tendency to break along plates of Weak bonding o Produces flat, shiny surfaces - Fracture o Absence of cleavage when a mineral is broken - Specific Gravity o Weight of mineral divided by the weight of an equal volume of water o Average = 2.7 g/cm3- Other Properties o Magnetism  (-Magnetite) o Reaction to hydrochloric acid  (-Dolomite) o Double refraction (shadow effect) (-Calcite) o Taste  (-Halite)o Smell  (-Sulfur) REVIEW QUESTIONS: Which diagnostic property is the least reliable- Color  impurities Streak of a mineral will always be the same as its color - False Polymorphs have the same composition but different crystalline structure- True Minerals- Nearly 4000 different minerals- Rock forming minerals o Only a few dozen memberso Made of the most common elements in the Earth’s crust Mineral Groups - Silicates (SiO4)o Most important mineral group o Compromise most rock-forming mineralso Very abundant due to large percentage of silicon and oxygen in the Earth’s crust o Silicon-Oxygen tetrahedron: fundamental building block o Four oxygen ions surrounding a smaller silicon ion Tetrahedral forms - By combining the SiO4tetrahedra together in different ways, we can make different minerals Categories of Silicate (SiO4) Minerals - Mafic: o Simpler SiO4 structure o Dark colored; more dense o Contain iron and magnesium o EX: Olivine, Biotite, Amphibole - Felsic: o More complex SiO4 structure o Light colored; less dense o No iron or magnesium o EX: Quartz, Feldspar, Muscovite Non-Silicate Minerals - Only 8% of the Earth’s crust - Many non-silicate minerals have important economic value - Examples: o Hematite (oxide mined for ion ore) o Halite (halide mined for salt)o Sphalerite (sulfide mined for zinc