Cumulative mineralogy questions

 

Potential questions are those that will be important for Petrology so important to ÒrefreshÓ your memory of. These are topics covered on the previous two tests (but not all the questions on these tests):

From test 1:

Definition of a mineral

GibbÕs Phase rule, degrees of freedom

 

From test 2:

Solid solution, cations involved, minerals involved

Equilibrium vs. fractional crystallization

Peritectic phase diagram

Optics: what is polarized light, index of refraction, isotropic vs. anisotropic minerals, birefringence, crystal systems and optic characteristics, how to ID a uniaxial or biaxial postive or negative mineral, length slow or fast, definition of 2V, question 22 of test 2 in any version (postive or negative, uniaxial or biaxial)

 

 

Last 5 weeks of class

¥KNOW MINERAL FORMULAE!!

¥EXPECT A QUESTION TO DESCRIBE THE MAJOR SILICATE STRUCTURES IN GENERAL TERMS AND GIVE AN EXAMPLE OF A MINERAL IN THAT GROUP

 

Microprobe vs CL vs. XRD: information that we can glean from each machine and basics

            for how the machines work

Phyllosilicates: all are hydrous, all with SiO4,

            octahedral sheets: trioctahedral and dioctahedral, ideal formulas of these layers

            tetrahedral sheets: ideal formula, basal oxygen, apical oxygen

            how to join tetrahedral and octahedral sheets: remove OH-, insert apical oxygen

            TO or 1:1 layers, know the dioctahedral and trioctahedral TO sheet silicates

            TOT or 2:1 layers, know the dioctahedral and trioctahedral TOT sheet silicates

            TOT with cation structures, know the dioctahedral and trioctahedral minerals

            TOT+O structure: chlorite, easy to make of alter biotite

Tectosilicates: reconstructive and displacive polymorphs of SiO2 phases

            increase of pressure favoring denser polymorph

            feldspars: 3 endmembers, 4 membered rings of tetrahedra

            slow cooling path of alkali feldspars: sanidine, orthoclase, microcline

            exsolution in alkali feldspar

Inosilicates:

            single chains Si:O = 1:3, pyroxene quadrilateral and solid solution, what                  orthpyroxene is vs. clinopyroxene, TOT structure with M2 cation linking                ÒI beamsÓ

            pyroxenoids: chains of Si tetrahedra are distorted w/ bigger repeat distances

            double chains Si:O = 4:11, orthoamphibole vs. clinoamphibole, TOT structure                   

forming the Òdouble-wide I beamsÓbonded through the M4 AND A cations.

            relationship between pyroxenes and amphiboles: dehydrate an amphibole to                   

                        pyroxene, alter a pyroxene to an amphibole

Sorosilicates:

            paired tetrahedra (bowtie silicates) with Si:O of 2:7. Easily described by chains of                   

                        aluminum octahedra

Cyclosilicates:

            6-fold rings of Si and Al tetrahedra. Si:O of 1:3. The rings are stacked on each               

                        other and bonded through other cations

Orthosilicates:

            Si:O of 1:4 since isolated tetrahedra. Group 1 is Si tetrahedra bonded                        laterally through other cations (Olivine garnet, zircon). Group 2 is easier                described by the non-Si cations like Al or Ti in chains or sheets of                 octahedra (Al-silicates, staurolite).

Clays: subgroup of phyllosilicates. TO minerals, TOT minerals and each can be                   dioctahedral and trioctahedral

Zeolites: framework silicates like quartz and feldspar with large voids in the framework.

            Zeolites can be hydrated/rehydrated, absorb other molecules, molecular sieving,                      cation exchange

Asbestos: any fibrous silicate with at least a ratio of 3:1 for length:width.

            Serpentine and amphibole asbestos. How formed? accommodates the mismatch

                        of the dimensions of the TO layers and they roll or curve

Nucleation and Crystallization: Undercooling, embryo formation, crystal growth to                        

                        reduce surface energy/solubility, reaches critical size

            Rate of cooling and number of nuclei and subsequently crystal size

            Slowest growing rates are the most prominent since fast-growing faces grow             

                        themselves out

            Texture results of 2-stage cooling

Structural defects and twinning

            Point defects: vacancy, mislocation, impurity (both interstitial and substitution)

            Line defects: edge and screw dislocation

            Planar defects: grain boundaries, stacking faults, antiphase boundaries

            Twinning by reflection or by rotation

            Contact twins, penetration twins, multiple twins, Carlsbad twinning, Albite twins

Color in minerals (know at least one theory and a mineral example)

            crystal field theory and the splitting of d-shell orbitals, Ruby due to Cr3+

            band theory (metallic or covalent bonding) (galena, diamond colorless or blue)

            charge transfer theory (sapphire due to Fe and Ti for Al)

            color centers (electron, hole) (fluorite)

Isostructuralism/Polymorphism

            isostructural/isostructural group

            polymorphism : reconstructive, displacive, order-disorder

            pseudomorphism