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GEOL 2311 Mineralogy Final Exam Name: Key Score: ________/ 200 Class Totals: Lecture: ____/480; Lab & Field Trip:____/511; Extra Credit: _____ Total Points:_____/991; Total %: ______; Final Grade________ Instructions for EXTRA CREDIT – for questions that ask you to circle the true statements, you will receive ½ pt extra credit for false statements that you can add or change a word or phrase to make the statement true (e.g., isometric minerals typically display anisotropic optical properties. isotropic ) First Third 1) Circle all the statements that are true about the definition of a mineral (3 pts) A) naturally occurring D) not necessarily fixed composition B) formed mostly by inorganic processes E) random chemical arrangement C) definite chemical composition F) highly ordered atomic structure 2) A mineral is named and classified mainly by what criteria? (circle one, 2 pts) a) its major cations b) its crystal class c) its major anionic component d) its space group symmetry 3) Name a mineral that contains the following common elements as a major chemical component. (8 pts; OK to name a mineral more than once) Si (silica) ______________________________ Al (aluminum) _____________________________ Ti (titanium) _____________________________ Mg (magnesium) ___________________________ Ca (calcium) _____________________________ K (potassium) ___________________________ P (phosphorous) ____________________________ Cl (chlorine) _____________________________ 4) Circle all the statements that are true about atoms, elements, and isotopes (3 pts) A) most mass of an atom is contained in the nucleus B) the nucleus is composed of protons and neutrons C) an element is defined by the number of protons, known as the atomic number D) in a stable, non-ionized atom, the number of protons, and electrons and neutrons are all equal. E) the isotopic number of an element is defined by the total number of protons and neutrons F) isotopes of a particular element have similar different atomic weights but different similar chemical properties Pg score _____ 5) The diagram below displays the types and number of electron subshell orbitals that exist in each of the principal electron shells (K, L, M, N…) of atoms. The element argon (atomic number 18) is a noble gas, which means that it has all of its subshell orbitals filled to capacity with electrons. Knowing this, what are the electron capacities of the S and the P subshell orbitals? (2 pts) S____2____ P ____6____ 6) Referring to the partial periodic table below for help, give the most common valence (or oxidation) state (e.g. +4, -1, …) for the following elements: (8 pts) Si _+4 Mg_+2 O __-2 Na_+1 Al_+3 Cl_-1 Mg_XX_ Ti _+4 (hint TiO2 is rutile) 7) Sulfur (S) can be an anion or a cation. What is its valance state as a cation?_+6 What is its valance state as an anion?__-2 (2 pts) 8) Circle the true statements about elements in the periodic table (3 pts) A) the electronegativity of elements increase across a row B) the 1st ionization potential of elements increase across a row Pg score _____ C) the atomic radius of cations increase decrease across a row D) the atomic radius of elements increase down a column E) the atomic radius of a particular element is fixed variable, regardless of the type and number of elements that surround it F) the elements in shaded boxes are considered non-metallic elements 9) Circle the true statements about bonding in minerals (4 pts) A) Covalent bonds are the weakest strongest type of bond B) Ionic bonds are formed from elements that exchange outer electrons whereas covalent bonds form by sharing outer electrons C) Different types of bonds commonly occur in the same mineral D) The greater the difference in electronegativity between two elements, the greater the tendency to create ionic bonds E) Metallic bonds can be thought of as element nuclei and inner electron shells in a “sea” of unbound electrons F) The strength of a bond is inversely proportional to its hardness G) Atomic nuclei and inner electron shells in a “sea” of unbound electrons is definition of Van der Waals metallic bonds H) Hydrogen bonds form by the polarization of the hydrogen-oxygen bond in a water molecule 10) Circle the true statements about packing of ions in minerals (3 pts) A) The coordination number is dependent on the cation:anion radius ratio B) A radius ratio of 1 favors octahedral (6-fold) 12-fold or close packed coordination C) Cubic coordination occurs for cations that have 8 nearest anion neighbors D) In most minerals, the main anionic element is iron oxygen E) Tetrahedral coordination occurs for cations that have 3 4 nearest anion neighbors F) Hexagonal-close packed coordination occurs where ions are stacked in an A-B-C A-B configuration 11) The strength of an ionic bond between a cation and and anion is proportional to its electrostatic valence (e.v.), which is defined as what? (circle one, 2 pts) A) the ratio of the valence number of the cation to its coordination number. B) the ratio of the valence numbers of the cation and anion C) the cation/anion radius ratio D) the difference between the valence numbers of the cation and anion. 12) Circle the true statements about phase equilibrium of minerals (4 pts) A) A mineral is said to be in equilibrium with its environment when it is at its lowest energy for the conditions of pressure and temperature B) All substances strive to be at their greatest state of order disorder C) Variables such as mass and volume are dependent on the amount of material present D) Variables such as temperature, pressure, and compositional proportions are also not dependent on the amount of material present E) In a one component system, an invariant point, where the degrees of freedom are zero, occurs where two three phases are in equilibrium according to the phase rule (F = C – Φ + 2; this equation is correct). 0=1-3+2 Pg score _____ F) In a two-component phase diagram for igneous systems, compositions is typically plotted against pressure temperature G) Subsolidus exsolution is cause by unmixing of components in a solid solution mineral as it cools down and the atomic structure becomes more ordered H) Phase diagrams for metamorphic systems are typically compositional diagrams that show equilibrium mineral phases at a particular pressure and temperature. 13) Indicate for the six phases on this compositional diagram whether they show complete solid solution, limited solid solution, and no solid solution? (6 pts) Tridymite - No Albite - Complete Orthoclase - Complete Nepheline - Limited Leucite - Limited Kalsilite - Limited Second Third 14) Circle the true statements about external crystal symmetry (4 pts) A) External crystal symmetry involves symmetry operations that lack translation B) The main external symmetry operations are rotation axes, center of symmetry and rotoinversion. And mirror planes C) There are 64 32 possible combinations of symmetry operations that define external symmetry of crystals D) The 222 point group (or crystal class) occurs in triclinic orthorhombic crystal system E) Crystals containing a combination of 4-fold, 3-fold and 2-fold rotation axes can only occur in the isometric crystal system F) Mirror planes (m) perpendicular to a rotational axis (#) is portrayed in the Hermann-Maugin notation by #/m G) Six-fold and three-fold rotation axes are common in the hexagonal system H) Isometric crystals have the greatest symmetry, and tetragonal triclinic crystals have the least symmetry. 15) Give the Hermann-Maugin notation for these tetragonal point groups (3 pts) 422 4/m2/m2/m 4mm Pg score _____ 16) Indicate which crystal system corresponds to each point group (4 pts) Point Group Crystal System 4mm Tetragonal 622 Hexagonal 4/m32/m Isometric 2/m Monoclinic 17) Circle the true statements about crystallographic axis and crystal systems (3 pts) A) Isometric crystals have mutually perpendicular axes of unequal lengths B) Hexagonal crystals have 4 axes, one (C) being different length than the other 3 C) Triclinic crystals have non-perpendicular axes of unequal length D) Tetragonal crystals have mutually perpendicular axes with two of equal length E) Monoclinic crystals have axes of unequal length and two that have a non-90° angle F) Orthorhombic crystals have mutually perpendicular axes of unequal lengths 18) What crystal face would qualify as the “unit face” in this crystal? (give face intercepts) (2 pts) 1 :1:1 19) Label the Miller indicies of the shaded faces for the three crystals (3 pts) Miller Indicies (1 0 1 0) ( 1 1 2 0) (1 1 2 1) Pg score _____ 20) What is the Miller index of the upper face (2 pts) (1/2 : 1/2 : 3/2)*2 = 1 : 1 : 3 21) What is the zone axis of faces m’, a, m, and b? (2 pts) [001] 22) Circle the true statements about twinning (3 pts) A) Twins are symmetrical intergrowth of two or more crystals related to a symmetry operation (twin element) that is otherwise absent in a single crystal B) Twin elements include mirrors, rotation axes (usually 2-fold) and roto-inversion C) Penetration twins form by reflective symmetry across a mirror plane rotation axes D) Contact twins form by rotational axes mirror plane/reflection symmetry E) Albite twinning is a type of multiple polysynthetic twinning F) Twinning only occurs in the isometric all crystal systems 23) Circle the true statements about 2D lattice symmetry (3 pts) A) A 2D unit cell is defined as the smallest grouping that define the basic ordering of an array of motifs or atoms. B) Only More than one type of unit cell can be defined in a 2D array C) Besides translation, screw axes glide lines are the other type of symmetry operation that distinguishes 2D lattice symmetry from point group symmetry of single crystals D) A rectangular plane lattice has orthogonal axes of unequal length E) Hexagonal plane lattices involve 3- or 6-fold rotation axes F) Glide lines involve mirror line and translation symmetry operations 24) Screw axes involve a combination of what two symmetry operations? (2 pts) rotation and translation Pg score _____ 25) Determine which of the 17 possible plane groups of 2D symmetry illustrated below applies to the two tessellation drawings on the next page. (2 pts) A) P2gg B) P6 Also, on each drawing, outline a unit cell and draw the symmetry elements contained within it. (6 pts) Pg score _____ 26) Match the 3D space group with the crystal system (11 pts) Space Group Crystal System F23 Isometric R3m Hexagonal P2/b21/c21/m Orthorhombic C2/m Monoclinic P42/m21/b2/c Tetragonal F4132 Isometric P63mc Hexagonal P4/m Tetragonal P1 Triclinic I212121 Orthorhombic I43d Isometric Last Third 27) Circle the true statements about the nature of light (6 pts) A) Light is a form of electromagnetic radiation B) Light can be characterized as a transverse wave form that travels in a straight line C) The frequency amplitude of light is manifest in the brightness of the light D) The velocity of light is its wavelength multiplied by its frequency E) Light speeds up slows down as it passes through denser substances F) The short long wavelength of visible light is in the red end of the spectrum 28) Circle the true statements about reflection, refraction, and relief (8 pts) A) Light is reflected at the same angle as the incident angle B) Refraction occurs when light passes from one substance into another and results in its changing velocity and being bent. C) The index of refraction measures the degree to which light is slowed down relative to the speed of light in a vacuum D) The critical angle of refraction is the incident angle at which the light will not be bent be reflected E) A mineral in an oil grain mount will show high relief only if it has a higher different index of refraction than the oil F) The dark outline of a mineral with high relief is caused by the refraction of light at the grain boundary G) In a Becke line test, the bright line moves toward the substance with the lower higher index of refraction H) In a grain mount where the index of refraction of the oil and the mineral are similar, one might observe a dispersion of the color spectrum at the grain boundaries. 29) What does an optical indicatrix portray in a mineral? (2 pts) It is a 3-d map of how the index of refraction of light varies with vibration direction in a mineral Pg score _____ 30) How can isotropic minerals be recognized under the microscope? (2 pts) They will be fully extinct under cross polarized light 31) Name two ways anisotropic minerals can be recognized under the microscope?(2 pts) It will display interference colors under cross polarized light It goes to extinction 4 times in a 360° rotation of the stage 32) For these uniaxial indicatricies: A) What crystal systems display this type of optics? (2 pts) uniaxial B) What is the sign of the indicatrix on the right? (1 pt) + C) What is another name for the C-axis (1 pt) optic axis or the ε vibration direction D) Is light vibrating in the ω direction the fast or slow ray in the left diagram? (1 pt) slow 33) Circle the true statements about optical properties of anisotropic minerals (8 pts) A) Interference colors indicate the retardation of light which is a product of birefringence and the thickness of the mineral B) A particular mineral of a constant thickness will always show the same variable interference colors regardless of depending on its orientation C) Maximum birefringence is the difference in the maximum and minimum index of refraction of a mineral D) When birefringence = 0, the mineral is sliced through principal circular section of the indicatrix E) To find an optic axis figure, one searches for a mineral that displays the highest lowest interference colors. F) A random section through the indicatrix shown in question 32 will always have one of the vibration directions parallel to ω. 34) For the figure to the right (1 pt each): A) What is this optic figure? (circle one) unixial optic axis biaxial optic axis uniaxial flash figure acute bisectrix B) What are the black bars called? isogyres C) If this figure has a positive sign, in which quadrants will the colors go down when a gypsum plate is inserted? NW & SE D) The color rings that encircle the cross are called isochromes and represent what ? Zones of equal retardation Pg score _____ 35) For the figures A & B below of sections through different biaxial indicatricies (1 pt each) A) Which displays a positive sign? A B) What plane lies perpendicular to each optic axis? Circular section C) In which will the Y axis be closer in length to the X axis? A A B 36) For this negative biaxial mineral, indicate the section that will (1 pt ea.) A) Give an optic axis figure YC B) Give an acute bisectrix figure YZ C) Give an obtuse bisectrix figure XY D) Show maximum birefringence XZ E) Show intermediate interference colors Any other than XZ or YC 37) By what two methods can the 2V angle of a biaxial mineral be estimated? (2 pts) 1) Curvature of the isogyre 2) Separation of the isogyres Pg score _____ 38) Name the types of extinction angles that would be generated by these three crystal configurations (3 pts) Symmetrical Parallel Inclined 39) Name three types of minerals that occur as metallic native elements (3 pts) gold, silver, copper, platinum, palladium, osmium, iridium, iron 40) Name 4 metals for which sulfide minerals are the most common source of ore (4 pts) Copper, iron, nickel, lead, zinc, cobalt, molybdenum, mercury 41) Name two copper-bearing sulfide minerals (2 pts) Chalcopyrite, covellite, chalcocite, diginite, bornite 42) The spinel group of oxides has the general formula of XY2O4. A) Cations of what valence state typically occupy the X site +2 (1pt) B) Give an example of such an cation Fe+2, Mg, Be (1pt) C) Cations of what valence state typically occupy the Y site +3 (1pt) D) Give an example of such an cation Fe+3, Al, Cr (1pt) 43) Red corundum is ruby; blue corundum is sapphire. What attribute of corundum makes these minerals good gemstones? (1 pt) Hardness ~9 44) What is the main anionic component of hydroxide minerals? (OH)- (1 pt) Name a type of hydroxide mineral manganite, brucite, gibbsite, goethite, diaspore, bauxite (1 pt) 45) Name an element that is a common anion in halides Cl, F, I, Br (1 pt) Name a type of halide mineral halite, fluorite, sylvite (1 pt) 46) What common feature does carbonate, sulfate, and phosphate minerals share? (1 pt) Have anionic complexes Pg score _____ 47) What is a common characteristic of most carbonates that aids in their identification? (1 pt) hexagonal, soft, will effervesce with acid if scratched 48) What are two subtypes of sulfates? (2 pts) hydrous and anhydrous 49) What is the net charge of the PO4 anionic complex that occurs in phosphate minerals? (1 pt) -3 50) What is the basic building block of all silicate minerals? (1 pt) silicon tetrahedra 51) Give two reasons why the Si-O bond is so strong in silicate minerals (2 pts) 1) it is a partially covalent bond 2) it has a high electrostatic valence (4/4 ~ 1) 52) Why don’t silica tetrahedral share edges or faces? (2 pts) repulsive forces of the highly charged Si +4 cations 53) Match the silicate group name and the SiO unit composition to each silicon tetrahedral arrangement. And name one common mineral from each group (21 pts) Si Gp: Nesosilicates SiO form: SiO4 Mineral Si Gp: Inosilicate double Si Gp: Sorosilicate SiO form : Si4O11 SiO form: Si2O7 Mineral Mineral Si Gp: Cyclosilicate SiO form: SiO3 Mineral Si Gp Inosilicate single SiO form: Si2O6 Mineral Si Gp: Phyllosilicate SiO form: Si2O5 Mineral Si Gp: Tectosilicate SiO form: SiO2 Mineral Silicate group names: sorosilicates, tectosilicates, nesosilicates, inosilicates (single), inosilicates (double), phyllosilicates, cyclosilicate Si-O unit compositions: SiO2, SiO4, Si2O7, SiO3, Si2O6, Si4O11, Si2O5, 54) What is the main attribute by which pyroxenes are distinguished from amphiboles? (1 pt) Pyx - 90° cleavage; Amph – 120/60° cleavage Pg score _____