Introduction to MineralogyDr. Tark Hamilton

Chapter 4: Lecture 16The Chemical Basis of Minerals

(Perovskite & Spinels)

Camosun College GEOS 250

Lectures: 9:30-10:20 M T Th F300

Lab: 9:30-12:20 W F300

Perovskite CaTiO3 Structure CCP Orthorhombic 2/m2/m2/m, dipyramidal

Ti+4 octahedralSharing apices

Large A site cationReplaces ¼ of Oxygen

Structure of Mesosphere!

Ettringer-Bellerberg Mt.,Germany~1mm - Stephan Wolfsried

Arborescent Perovskite CaTiO3

Stoltz Quarry, Graulai, Germany

Dysanalite (Nb,REE)Oka, PQ w/ Calcite &

Monticellite P.Cristofono

Lohley, Germany,Sephan Wolfsried

Graulai, Germany,Sephan Wolfsried

Spinel AB2O4 Structure (~CCP)

Alternate layers parallel (111)Octahedral &

Octahedral - Tetrahedral

Oct

Oct

Oct & Tet

Perpendicular to (111)after Waychunas (1991)

CCP with1/8 Tetrahedral = A¼ Octahedral = B

Normal Spinel: B all OctInverse Spinel: B ½ Tet

View along Four-fold Symmetry Axis (001 Plane)

                                                                                                                                       

Spinel Structure (001) after Steven Dutch

Filled octahedra form criss-cross rows with alternating layers of parallel rows offset as shown on the right side of the diagram. The square holes

enclosed by the rows of octahedra are filled with tetrahedra

Layer 1

Layer 3

                      

         Figure 1-a: Two kinds of occupied tetrahedral sites in spinel sub-cell a. A is in green and O is in red.

                   

            Figure 1-b: Occupied octahedral site in spinel sub-cell b. B is in gray, and O is in red.

                          

            Figure 2: Arrangement of structure a and b in one unit cell. shaded one represents structure a, while white one represents b.

Spinels: 2 Types of sub-unit cells

Gary Wulfsberg, Inorganic Chemistry, (2000)

Spinel Formulae: A+2B+32O4 > (Y+4X+2

2O4

Olivine ~12% less dense: transition 360-610km)

• Normal Spinels:• Spinel: MgAl2O4

• Hercynite: FeAl2O4

• Gahnite: ZnAl2O4

• Franklinite: ZnFe+32O4

• Chromite: FeCr2O4

• Magnesiochromite MgCr2O4

• LiMn2O4 Lithium battery

• Inverse Spinels:• Magnetite: Fe+2Fe+3

2O4

• Ulvospinel: Fe+22Ti+4O4

• Ni+2Fe+32O4

• Co+2Fe+32O4

• Ferrofluids paramagnets

• Thiospinels:• Greigite: Fe+2Fe+3

2S4

• Cuprous Ferrites CuCr2S4

0.8 < A < 1.1 Ang. (Mg, Fe, Mn, Zn, & Cu) & 0.75 < B < 0.9 Ang. (Ti, Fe, Al, & Co) Magnetospirillum magnetotacticum makes Greigite magnetosomes for navigation

Franklinite, Sterling Hill withZincite & Calcite M.Baum 1993

8mm Magnetite with EpidoteSpeen Ghar, Afghanistan

Rob Lavinsky

Named for ”Magnesia”, Greece

Named for Ben Franklin & Franklin Furnace

Spinels: Mogok, MyanmarRob Lavinsky

Chromite bands in serpentinized DuniteSommergraben, Austria, Franz Bernhard

C. Thompson

Greigite (Fe2+Fe3+2S4)

infilling wood

NGHP: SiltKrishna-Godarvi Basin

Calcite

Exsolution of Cubic “Fe-Ti Spinel”& Hexagonal Imeno-Hematite (Norway)

Oxygen Linkages in Common Silicates

Nesosilicates: OlivineGarnet, ZirconKyanite (SiO4)-4

Sorosilicates: “Pyro” Lawsonite, Epidote

Melilite, HemimorphiteVesuvianite (Si2O7)-6

Cyclosilicates: BerylCordierite, BenitoiteTourmaline (Si6O18)-12

I-Inosilicates: EnstatiteAcmite, Augite, Jadeite Wollastonite (Si2O6)-4

II-Inosilicates:Hornblende

Arfvedsonite(Si4O11)-6

Phyllosilicates:ParagoniteKaolinite

Polylithionite(Si2O5)-2

Tectosilicates:Quartz, Tridymite

Coesite (SiO2)0