Introduction to Mineralogy Dr. Tark Hamilton Chapter 4: Lecture 13 The Chemical Basis of Minerals (Parsimony & Isostructural Minerals) Camosun College GEOS 250 Lectures: 9:30-10:20 M T Th F300 Lab: 9:30-12:20 W F300

#5 - Principle of Parsimony # of contrasting elements are small because there are few anion or cation sites Complex compositions tend toward several constituents (cations) in the same kind of site This is termed solid solution: Fe for Mg, Si for Al, Ca for Na (definite not exact compositions) Goldschmidt’s rules say ions have to be similar size +/-15% and +/- 1 charge unit

Limited Types of Coordination Octahedral – Na & Cl Octahedral – Ca Tetrahedral – F Octahedral – empty Tetrahedral - S Halite Fluorite Sphalerite

Halite: Hesse, Germany S. Menig 2005, Saskatchewan Rob Levinsky 4/m 3 2/m Hexoctahedral Cubes Cubic cleavage on (001) Evaporite deposits, Salt domes Bedded sediments Halite named by J.D. Dana for Greek αλς “sea” Muhlhausen Alsace, France John Betts 2002; Christopher O’Neill

Fluorite: Rogerly Mine, Weardale, Durham Co. Pennines Wales, Jesse Fisher /m 3 2/m Hexoctahedral Cubes with Penetration twins (111) Cleavage octahedral The term fluorescence is derived from fluorite, which will often exhibit this effect when Y & Ce Substitute for Ca ions Ore of Fluorine Production of HF Flux in Steel & Glass Greisens, Granites Pegmatites & Gangue in Hi T Pb-Zn ores Octahedra Catamarca Argentina J.C. Lodovici Tetrahexahedron Nilaw-Kolum Afghanistan Fabre Minerals

Mineral Names - Trivial Pursuits! Halite – Greek, halos for salt, mineral of health Fluorite – Latin fleure to flow, melts easily, flux Sphalerite – Greek treacherous, zincblende, German “blind”, decieving,rubyzinc or blackjack

Sphalerite: 43m Hextetrahedral v.Marmatite Elmwood Mine TN, John Betts 2003 var. Ruby-blende, Taz. Aus.R. Bottrill 2006 CdS Greenockite coating, Tazmania, viccloete

Sphalerite Think about those empty octahedra of Zn! X3 to x10 thermal and electrical conductivity compared to other sulphides With Fe substitution, darkens (blackjack), reflects more & enhances magnetic susceptibility w/ Pyrrhotite Fe1-xS, Fe-Zn a geothermometer, Main ore of Cd, isostructural w/Greenockite CdS alters to Goslarite ZnSO 3 or Smithsonite ZnCO 3

Parsimony - Complex compositions tend toward several constituents (cations) in the same kind of site Monoclinic Amphiboles: Hornblende, Richterite, Actinolite, Tremolite, Glaucophane, Riebeckite (Ca,Na) 2-3 (Mg,Fe,Al) 5 Si 6 (Si,Al) 2 O 22 (OH) 2 For chemical calculations sometimes O 23

Amphibole Polyhedral Sites Projected along a - axis J.J Papike, 1969 Si +4, Al +3 Mg Fe, Mn Al +3, Fe +3 Ti +4 Ca +2, Na + Ca +2, K + T2

Riebeckite :[ ][Na 2 ][Fe 2+ 3 Fe 3+ 2 ][(OH) 2 ][Si 8 O 22 ] Golden Horn Batholith, Washington Pass, ROM Richterite: Na[CaNa][Mg 5 ][(OH) 2 ][Si 8 O 22 ] Mt. Ngongotaha Rotorua NZ Magnesiohornblende : [Ca 2 ][Mg 4 Al][(OH) 2 ][AlSi 7 O 22 ] Eifel Mtns Rhineland Germany J. Weissmann 2008 Chromian Tremolite: [Ca 2 ][Mg 5 ][(OH) 2 ][Si 8 O 22 ] Haliburton ON John Betts 2001

Isostructural Minerals UO 2 & CaF 2 (Uraninite & Fluorite, Oct/Tet) (different in solutions, Linear & Oct/Cubic, different energy or they wouldn’t dissolve!) NaCl Halite & MgO Periclase & PbS Galena & MnS Alabandite & AgCl Chlorargyrite & TiN Osbornite (named after Donny & Marie?) Stishovite SiO 2 & Rutile TiO 2 are both octahedral, for Silicon this takes GPa’s of P Isostructural Groups: Barite (sulphates), Calcite (Carbonates) Aragonite (Carbonates)

Uraninite & Gummite Great Bear Lake, NWT M Arliguie UO 2 Haliburton ON John Betts 2001 Uraninite radiation damage halo Parfurbwirt, Austria Chris Auer, 1984