Chapter 14 Classification and names of minerals

Mineral varieties: isomorphism Garnets Garnets Same crystal system and morphologySame crystal system and morphology Considerable difference in chemical composition and with that density, hardness, refractive index and unit cell parameters differConsiderable difference in chemical composition and with that density, hardness, refractive index and unit cell parameters differ Plot compositions between 3 end members in pyralspyte garnet series (Fe, Mg, Mn-rich) on ternary diagramPlot compositions between 3 end members in pyralspyte garnet series (Fe, Mg, Mn-rich) on ternary diagram Composition in reality range between these components and general formula is (Fe, Mg, Mn) 3 Al 2 (SiO 4 ) 3Composition in reality range between these components and general formula is (Fe, Mg, Mn) 3 Al 2 (SiO 4 ) 3 The relative ratios of Fe, Mg, Mn differ for the different garnets: pyrope, spessartite, almanditeThe relative ratios of Fe, Mg, Mn differ for the different garnets: pyrope, spessartite, almandite Uvarovite series garnets have the endmembers: andradite, grossular, ugranditeUvarovite series garnets have the endmembers: andradite, grossular, ugrandite Carbonates Carbonates Calcite, magnesite, rhodochrosite, sideriteCalcite, magnesite, rhodochrosite, siderite Compositions vary but same morphologyCompositions vary but same morphology Most carbonates rather close to end-member compositionsMost carbonates rather close to end-member compositions Carbonates with intermediate compositions has different morphology than above mineralsCarbonates with intermediate compositions has different morphology than above minerals

Mineral varieties: polymorphism Different mineral species: different morphology but same chemical compositions Different mineral species: different morphology but same chemical compositions SiO 2 minerals (silica minerals): SiO 2 minerals (silica minerals): quartztrigonal stishovitetetragonal tridymitehexagonal etc.

Elementary chemical composition 4000 mineral species with individual mineral names (currently) 4000 mineral species with individual mineral names (currently) Within species different polytypes: Within species different polytypes: Quartz: amethyst, citrine, rosequartz, etc.;Quartz: amethyst, citrine, rosequartz, etc.; Beryl: emerald (Cr-rich); aquamarine (Fe-rich)Beryl: emerald (Cr-rich); aquamarine (Fe-rich) Common minerals contain abundant elements: O, H, Si, Al, Na, Mg, Ca, Fe, K Common minerals contain abundant elements: O, H, Si, Al, Na, Mg, Ca, Fe, K Lithofile, chalcofile, siderofile, halogenofile, atmofile Lithofile, chalcofile, siderofile, halogenofile, atmofile

SilicatesGroup Alternate name DescriptionMinerals Nesosilicates Ortho- or island Isolated tetrahedron Olivine, garnet Sorosilicates Double-isolated tetrahedron Epidote CyclosilicatesRing Tetrahedrons linked into isolated ring Beryl, tourmaline, cordierite Inosilicates Single chain Tetrahedrons link in infinite single chain Pyroxenes Double chain Tetrahedrons link in infinite double chain Amphiboles PhyllosilicatesSheet Tetrahedrons link in infinite sheet Micas, clay minerals TectosilicatesFramework Tetrahedrons link in infinite network Quartz, feldspars, feldspathoids

Classification of minerals Genetic: Genetic: According to principal processes by which minerals are formedAccording to principal processes by which minerals are formed Not mineralogical and problematicNot mineralogical and problematic Geochemical Geochemical Based on principal chemical elementsBased on principal chemical elements Irrational: minerals that consist of many elements?Irrational: minerals that consist of many elements? Crystal chemical Crystal chemical Functional relationship between chemical compositionFunctional relationship between chemical composition AcceptableAcceptable Geochemical and crystal chemical Geochemical and crystal chemical Very usefulVery useful

ClassificationClass Mineral group Minerals 1 Native elements Au, As, S 2 Sulphides and sulphosalts Galena, Realgar, arsenides 3Halides Fluorite, Halite 4 Oxides and hydroxides Chromite, Bismite 5Silicates Neso-, Soro-, Cyclo-, Ino- (Single/Double), Phyllo-, Tecto- 6BoratesBoracite 7Carbonates Calcite, Dolomite 8 Phosphates, arsenates, vanadates Apatite, Descloizite 9 Sulphates, selenates, tellurides Gypsum 10 Wolframates, Molibenates Wolframite, wulfenite 11ChromatesCrocoite 12 Nitrates, Iodates Salpetre

Chapter 15 Mineral identification of hand specimens Self study and watch video on Blackboard: Identification of minerals