Transcript Mineralogy Lecture 16

Introduction to Mineralogy
Dr. Tark Hamilton
Chapter 4: Lecture 16
The 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
Structure of Mesosphere!
Large A site cation
Replaces ¼ of Oxygen
Ti+4 octahedral
Sharing apices
Arborescent Perovskite CaTiO3
Stoltz Quarry, Graulai, Germany
Graulai, Germany,
Sephan Wolfsried
Dysanalite (Nb,REE)
Ettringer-Bellerberg Mt.,Germany
~1mm - Stephan Wolfsried
Oka, PQ w/ Calcite &
Monticellite P.Cristofono
Lohley, Germany,
Sephan Wolfsried
Spinel AB2O4 Structure (~CCP)
Alternate layers parallel (111)
Octahedral &
Octahedral - Tetrahedral
Oct
Oct & Tet
Oct
CCP with
1/8 Tetrahedral = A
¼ Octahedral = B
Perpendicular to (111)
after Waychunas (1991)
Normal Spinel: B all Oct
Inverse Spinel: B ½ Tet
Spinel Structure (001) after Steven Dutch
Layer 1
View along Four-fold Symmetry Axis (001 Plane)
Layer 3
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
Spinels: 2 Types of sub-unit cells
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 subcell 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.
Gary Wulfsberg, Inorganic Chemistry, (2000)
Spinel Formulae: A+2B+32O4 >
(Y+4X+22O4 Olivine ~12% less dense: transition 360-610km)
• Normal Spinels:
• Inverse Spinels:
•
•
•
•
•
•
•
•
•
•
•
•
Spinel: MgAl2O4
Hercynite: FeAl2O4
Gahnite: ZnAl2O4
Franklinite: ZnFe+32O4
Chromite: FeCr2O4
Magnesiochromite MgCr2O4
LiMn2O4 Lithium battery
Magnetite: Fe+2Fe+32O4
Ulvospinel: Fe+22Ti+4O4
Ni+2Fe+32O4
Co+2Fe+32O4
Ferrofluids paramagnets
• Thiospinels:
• Greigite: Fe+2Fe+32S4
• 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
Named for ”Magnesia”, Greece
C. Thompson
Spinels: Mogok, Myanmar
8mm Magnetite with Epidote
Rob Lavinsky
Franklinite, Sterling Hill with
Zincite & Calcite M.Baum 1993
Speen Ghar, Afghanistan
Rob Lavinsky
Chromite bands in serpentinized Dunite
Sommergraben, Austria, Franz Bernhard
Named for Ben Franklin & Franklin Furnace
Greigite (Fe2+Fe3+2S4)
infilling wood
Calcite
NGHP: Silt
Krishna-Godarvi Basin
Exsolution of Cubic “Fe-Ti Spinel”
& Hexagonal Imeno-Hematite (Norway)
Oxygen Linkages in Common Silicates
Nesosilicates: Olivine
Garnet, Zircon
Kyanite (SiO4)-4
Sorosilicates: “Pyro”
Lawsonite, Epidote
Melilite, Hemimorphite
Vesuvianite (Si2O7)-6
Cyclosilicates: Beryl
Cordierite, Benitoite
Tourmaline (Si6O18)-12
I-Inosilicates: Enstatite
Acmite, Augite, Jadeite
Wollastonite (Si2O6)-4
II-Inosilicates:
Hornblende
Arfvedsonite
(Si4O11)-6
Phyllosilicates:
Paragonite
Kaolinite
Polylithionite
(Si2O5)-2
Tectosilicates:
Quartz, Tridymite
Coesite (SiO2)0