Silikatlar Mineral Structures Mineral Structures Mineral Structures Silicates are classified on the basis of Si Silicates are classified on the basis of Si- -O polymerism O polymerism The culprit: the [SiO The culprit: the [SiO 4 4 ] ] 4 4- - tetrahedron tetrahedronMineral Structures Mineral Structures Silicates are classified on the basis of Si Silicates are classified on the basis of Si- -O polymerism O polymerism [SiO [SiO 4 4 ] ] 4 4- - Independent tetrahedra Independent tetrahedra Nesosilicates Nesosilicates Examples: olivine garnet Examples: olivine garnet [Si [Si 2 2 O O 7 7 ] ] 6 6- - Double tetrahedra Double tetrahedra Sorosilicates Sorosilicates Examples: lawsonite Examples: lawsonite n[SiO n[SiO 3 3 ] ] 2 2- - n = 3, 4, 6 n = 3, 4, 6 Cyclosilicates Cyclosilicates Examples: benitoite BaTi[Si Examples: benitoite BaTi[Si 3 3 O O 9 9 ] ] axinite Ca axinite Ca 3 3 Al Al 2 2 BO BO 3 3 [Si [Si 4 4 O O 12 12 ]OH ]OH beryl Be beryl Be 3 3 Al Al 2 2 [Si [Si 6 6 O O 18 18 ] ]Mineral Structures Mineral Structures Silicates are classified on the basis of Si Silicates are classified on the basis of Si- -O polymerism O polymerism [SiO [SiO 3 3 ] ] 2 2- - single chains single chains Inosilicates Inosilicates [Si [Si 4 4 O O 11 11 ] ] 4 4- - Double tetrahedra Double tetrahedra pryoxenes pyroxenoids pryoxenes pyroxenoids amphiboles amphibolesMineral Structures Mineral Structures Silicates are classified on the basis of Si Silicates are classified on the basis of Si- -O polymerism O polymerism [Si [Si 2 2 O O 5 5 ] ] 2 2- - Sheets of tetrahedra Sheets of tetrahedra Phyllosilicates Phyllosilicates micas talc clay minerals serpentine micas talc clay minerals serpentineMineral Structures Mineral Structures Silicates are classified on the basis of Si Silicates are classified on the basis of Si- -O polymerism O polymerism [SiO [SiO 2 2 ] 3 ] 3- -D frameworks of tetrahedra: fully polymerized D frameworks of tetrahedra: fully polymerized Tectosilicates Tectosilicates quartz and the silica minerals feldspars feldspathoids zeolites quartz and the silica minerals feldspars feldspathoids zeolites low low- -quartz quartzTectosilicates Tectosilicates Stishovite Coesite ?- quartz ?- quartz Liquid Tridymite Cristobalite 600 1000 1400 1800 2200 2600 2 4 6 8 10 Pressure (GPa) Temperature o C After Swamy and Saxena (1994) J. Geophys. Res., 9 9, 11,787-11,794.Tectosilicates Tectosilicates Low Quartz Low Quartz 001 Projection Crystal Class 32 001 Projection Crystal Class 32 Stishovite Coesite ?- quartz ?- quartz Liquid Tridymite CristobaliteTectosilicates Tectosilicates High Quartz at 581 High Quartz at 581 o o C C 001 Projection Crystal Class 622 001 Projection Crystal Class 622 Stishovite Coesite ?- quartz ?- quartz Liquid Tridymite CristobaliteTectosilicates Tectosilicates Cristobalite Cristobalite 001 Projection Cubic Structure 001 Projection Cubic Structure Stishovite Coesite ?- quartz ?- quartz Liquid Tridymite CristobaliteTectosilicates Tectosilicates Stishovite Stishovite High pressure High pressure ? ? Si Si VI VI Stishovite Coesite ?- quartz ?- quartz Liquid Tridymite CristobaliteTectosilicates Tectosilicates Low Quartz Stishovite Low Quartz Stishovite Si Si IV IV Si Si VI VITectosilicates Tectosilicates Feldspars Feldspars Albite: Albite: Na NaAl AlSi Si 3 3 O O 8 8 Substitute two Substitute two Al Al 3+ 3+ for Si for Si 4+ 4+ allows Ca allows Ca 2+ 2+ to to be added be added Substitute Al Substitute Al 3+ 3+ for Si for Si 4+ 4+ allows allows Na Na + + or K or K + + to be to be added addedSiO SiO 4 4 tetrahedra polymerized into 2 tetrahedra polymerized into 2- -D sheets: [Si D sheets: [Si 2 2 O O 5 5 ] ] Apical O’s are unpolymerized and are bonded to other constituents Apical O’s are unpolymerized and are bonded to other constituents Phyllosilicates PhyllosilicatesTetrahedral layers are bonded to octahedral layers Tetrahedral layers are bonded to octahedral layers (OH) pairs are located in center of T rings where no apical O (OH) pairs are located in center of T rings where no apical O Phyllosilicates PhyllosilicatesOctahedral layers can be understood by analogy with hydroxides Octahedral layers can be understood by analogy with hydroxides Phyllosilicates Phyllosilicates Brucite: Mg(OH) Brucite: Mg(OH) 2 2 Layers of octahedral Mg in Layers of octahedral Mg in coordination with (OH) coordination with (OH) Large spacing along Large spacing along c c due due to weak van der waals to weak van der waals bonds bonds c cPhyllosilicates Phyllosilicates Gibbsite: Al(OH) Gibbsite: Al(OH) 3 3 Layers of octahedral Al in coordination with (OH) Layers of octahedral Al in coordination with (OH) Al Al 3+ 3+ means that means that only 2/3 of the VI sites may be occupied only 2/3 of the VI sites may be occupied for charge for charge- -balance reasons balance reasons Brucite Brucite- -type layers may be called type layers may be called trioctahedral trioctahedral and gibbsite and gibbsite- -type type dioctahedral dioctahedral a a 1 1 a a 2 2Phyllosilicates Phyllosilicates Kaolinite: Kaolinite: Al Al 2 2 [Si [Si 2 2 O O 5 5 ] (OH) ] (OH) 4 4 T T- -layers and layers and di diocathedral (Al ocathedral (Al 3+ 3+ ) layers ) layers (OH) at center of T (OH) at center of T- -rings and fill base of VI layer rings and fill base of VI layer ? ? Yellow = (OH) Yellow = (OH) T T O O - - T T O O - - T T O O vdw vdw vdw vdw weak van der Waals bonds between T weak van der Waals bonds between T- -O groups O groups Phyllosilicates Phyllosilicates Serpentine: Serpentine: Mg Mg 3 3 [Si [Si 2 2 O O 5 5 ] (OH) ] (OH) 4 4 T T- -layers and layers and tri triocathedral (Mg ocathedral (Mg 2+ 2+ ) layers ) layers (OH) at center of T (OH) at center of T- -rings and fill base of VI layer rings and fill base of VI layer ? ? Yellow = (OH) Yellow = (OH) T T O O - - T T O O - - T T O O vdw vdw vdw vdw weak van der Waals bonds between T weak van der Waals bonds between T- -O groups O groups Serpentine Serpentine Octahedra are a bit larger than tetrahedral Octahedra are a bit larger than tetrahedral match, so they cause bending of the T match, so they cause bending of the T- -O O layers (after Klein and Hurlbut, 1999). layers (after Klein and Hurlbut, 1999). Antigorite maintains a Antigorite maintains a sheet sheet- -like form by like form by alternating segments of alternating segments of opposite curvature opposite curvature Chrysotile does not do this Chrysotile does not do this and tends to roll into tubes and tends to roll into tubesSerpentine Serpentine The rolled tubes in chrysotile resolves the apparent The rolled tubes in chrysotile resolves the apparent paradox of asbestosform sheet silicates paradox of asbestosform sheet silicates S = serpentine T = talc S = serpentine T = talc Nagby and Faust (1956) Am. Mineralogist 41, 817-836. Veblen and Busek, 1979, Science 206, 1398-1400.Phyllosilicates Phyllosilicates Pyrophyllite: Pyrophyllite: Al Al 2 2 [Si [Si 4 4 O O 10 10 ] (OH) ] (OH) 2 2 T T- -layer layer - - di diocathedral (Al ocathedral (Al 3+ 3+ ) layer ) layer - - T T- -layer layer T T O O T T - - T T O O T T - - T T O O T T vdw vdw vdw vdw weak van der Waals bonds between T weak van der Waals bonds between T - - O O - - T groups T groups Yellow = (OH) Yellow = (OH)Chlorite: (Mg, Fe) Chlorite: (Mg, Fe) 3 3 [(Si, Al) [(Si, Al) 4 4 O O 10 10 ] (OH) ] (OH) 2 2 (Mg, Fe) (Mg, Fe) 3 3 (OH) (OH) 6 6 = T = T - - O O - - T T - - (brucite) (brucite) - - T T - - O O - - T T - - (brucite) (brucite) - - T T - - O O - - T T - - Very hydrated (OH) Very hydrated (OH) 8 8 , so low , so low- -temperature stability (low temperature stability (low- -T metamorphism T metamorphism and alteration of mafics as cool) and alteration of mafics as cool) Phyllosilicates PhyllosilicatesMineral Structures Mineral Structures Nesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Nesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Olivine (100) view blue = M1 yellow = M2 Olivine (100) view blue = M1 yellow = M2 b b c c projection projectionOlivine (100) view blue = M1 yellow = M2 Olivine (100) view blue = M1 yellow = M2 b b c c perspective perspective Nesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Olivine (001) view blue = M1 yellow = M2 Olivine (001) view blue = M1 yellow = M2 M1 in rows M1 in rows and share and share edges edges M2 form M2 form layers in a layers in a- -c c that share that share corners corners Some M2 Some M2 and M1 share and M1 share edges edges b b a a Nesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Nesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Olivine (100) view blue = M1 yellow = M2 Olivine (100) view blue = M1 yellow = M2 b b c c M1 and M2 as polyhedra M1 and M2 as polyhedraNesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Olivine Occurrences: Olivine Occurrences: ? ? Principally in mafic and ultramafic igneous and meta Principally in mafic and ultramafic igneous and meta- - igneous rocks igneous rocks ? ? Fayalite in meta Fayalite in meta- -ironstones and in some alkalic ironstones and in some alkalic granitoids granitoids ? ? Forsterite in some siliceous dolomitic marbles Forsterite in some siliceous dolomitic marbles Monticellite CaMgSiO Monticellite CaMgSiO 4 4 Ca Ca ? ? M2 (larger ion, larger site) M2 (larger ion, larger site) High grade metamorphic siliceous carbonates High grade metamorphic siliceous carbonatesNesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Garnet (001) view blue = Si purple = A turquoise = B Garnet (001) view blue = Si purple = A turquoise = B Garnet: A Garnet: A 2+ 2+ 3 3 B B 3+ 3+ 2 2 [SiO [SiO 4 4 ] ] 3 3 “Pyralspites” “Pyralspites” - - B = Al B = Al Py Pyrope: Mg rope: Mg 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 Al Almandine: Fe mandine: Fe 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 Sp Spessartine: Mn essartine: Mn 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 “Ugrandites” “Ugrandites” - - A = Ca A = Ca U Uvarovite: Ca varovite: Ca 3 3 Cr Cr 2 2 [SiO [SiO 4 4 ] ] 3 3 Gr Grossularite: Ca ossularite: Ca 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 And Andradite: Ca radite: Ca 3 3 Fe Fe 2 2 [SiO [SiO 4 4 ] ] 3 3 Occurrence: Occurrence: Mostly metamorphic Mostly metamorphic Some high Some high- -Al igneous Al igneous Also in some mantle peridotites Also in some mantle peridotitesNesosilicates: independent SiO Nesosilicates: independent SiO 4 4 tetrahedra tetrahedra Garnet (001) view blue = Si purple = A turquoise = B Garnet (001) view blue = Si purple = A turquoise = B Garnet: A Garnet: A 2+ 2+ 3 3 B B 3+ 3+ 2 2 [SiO [SiO 4 4 ] ] 3 3 “Pyralspites” “Pyralspites” - - B = Al B = Al Py Pyrope: Mg rope: Mg 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 Al Almandine: Fe mandine: Fe 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 Sp Spessartine: Mn essartine: Mn 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 “Ugrandites” “Ugrandites” - - A = Ca A = Ca U Uvarovite: Ca varovite: Ca 3 3 Cr Cr 2 2 [SiO [SiO 4 4 ] ] 3 3 Gr Grossularite: Ca ossularite: Ca 3 3 Al Al 2 2 [SiO [SiO 4 4 ] ] 3 3 And Andradite: Ca radite: Ca 3 3 Fe Fe 2 2 [SiO [SiO 4 4 ] ] 3 3 Occurrence: Occurrence: Mostly metamorphic Mostly metamorphic Pyralspites in meta Pyralspites in meta- -shales shales Ugrandites in meta Ugrandites in meta- -carbonates carbonates Some high Some high- -Al igneous Al igneous Also in some mantle peridotites Also in some mantle peridotites a a 1 1 a a 2 2 a a 3 3Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside: CaMg [Si Diopside: CaMg [Si 2 2 O O 6 6 ] ] b b a sin a sin ? ? Where are the Si Where are the Si- -O O- -Si Si- -O chains?? O chains??Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) b b a sin a sin ? ?Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) b b a sin a sin ? ?Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) b b a sin a sin ? ?Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) b b a sin a sin ? ?Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) b b a sin a sin ? ?Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Perspective view Perspective viewInosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca) SiO SiO 4 4 as polygons as polygons (and larger area) (and larger area) IV slab IV slab IV slab IV slab IV slab IV slab IV slab IV slab VI slab VI slab VI slab VI slab VI slab VI slab b b a sin a sin ? ?Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes M1 octahedron M1 octahedronInosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes M1 octahedron M1 octahedronInosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes M1 octahedron M1 octahedron (+) type by convention (+) type by convention (+)Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes M1 octahedron M1 octahedron This is a ( This is a (- -) type ) type (-)Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes T T M1 M1 T T Creates an “I Creates an “I- -beam” beam” like unit in the like unit in the structure. structure.Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes T T M1 M1 T T Creates an “I Creates an “I- -beam” beam” like unit in the like unit in the structure structure (+ ) (+ )The pyroxene The pyroxene structure is then structure is then composed of composed of alternating I alternating I- -beams beams Clinopyroxenes have Clinopyroxenes have all I all I- -beams oriented beams oriented the same: all are (+) the same: all are (+) in this orientation in this orientation (+ ) (+ ) (+ ) (+ ) (+ ) (+ ) (+ ) (+ ) (+ ) (+ ) Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes Note that M1 sites are Note that M1 sites are smaller than M2 sites, since smaller than M2 sites, since they are at the apices of the they are at the apices of the tetrahedral chains tetrahedral chainsThe pyroxene The pyroxene structure is then structure is then composed of composed of alternation I alternation I- -beams beams Clinopyroxenes have Clinopyroxenes have all I all I- -beams oriented beams oriented the same: all are (+) the same: all are (+) in this orientation in this orientation (+ ) (+ ) (+ ) (+ ) (+ ) (+ ) Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes (+ ) (+ ) (+ ) (+ )Tetrehedra and M1 Tetrehedra and M1 octahedra share octahedra share tetrahedral apical tetrahedral apical oxygen atoms oxygen atoms Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes The tetrahedral chain The tetrahedral chain above the M1s is thus above the M1s is thus offset from that below offset from that below The M2 slabs have a The M2 slabs have a similar effect similar effect The result is a The result is a monoclinic monoclinic unit cell, unit cell, hence hence clinopyroxenes clinopyroxenes Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes c c a a (+) M1 (+) M1 (+) M2 (+) M2 (+) M2 (+) M2Orthopyroxenes Orthopyroxenes have have alternating (+) and ( alternating (+) and (- -) ) I I- -beams beams the offsets thus the offsets thus compensate and result compensate and result in an in an orthorhombic orthorhombic unit cell unit cell This also explains the This also explains the double double a a cell dimension cell dimension and why orthopyroxenes and why orthopyroxenes have have {210} {210} cleavages cleavages instead of {110) as in instead of {110) as in clinopyroxenes (although clinopyroxenes (although both are at 90 both are at 90 o o ) ) Inosilicates: single chains Inosilicates: single chains- - pyroxenes pyroxenes c c a a (+) M1 (+) M1 ( (- -) M1 ) M1 ( (- -) M2 ) M2 (+) M2 (+) M2Pyroxene Chemistry Pyroxene Chemistry The general pyroxene formula: The general pyroxene formula: W W 1 1- -P P (X,Y) (X,Y) 1+P 1+P Z Z 2 2 O O 6 6 Where Where ? ? W = W = Ca Ca Na Na ? ? X = X = Mg Fe Mg Fe 2+ 2+ Mn Ni Li Mn Ni Li ? ? Y = Al Fe Y = Al Fe 3+ 3+ Cr Ti Cr Ti ? ? Z = Z = Si Si Al Al Anhydrous Anhydrous so high so high- -temperature or dry conditions temperature or dry conditions favor pyroxenes over amphiboles favor pyroxenes over amphibolesPyroxene Chemistry Pyroxene Chemistry The pyroxene quadrilateral and opx The pyroxene quadrilateral and opx- -cpx solvus cpx solvus Coexisting opx + cpx in many rocks (pigeonite only in volcanics) Coexisting opx + cpx in many rocks (pigeonite only in volcanics) Diopside Diopside Hedenbergite Hedenbergite Wollastonite Wollastonite Enstatite Enstatite Ferrosilite Ferrosilite orthopyroxenes clinopyroxenes pigeonite (Mg,Fe) (Mg,Fe) 2 2 Si Si 2 2 O O 6 6 Ca(Mg,Fe)Si Ca(Mg,Fe)Si 2 2 O O 6 6 pigeonite orthopyroxenes Solvus Solvus 1200 1200 o o C C 1000 1000 o o C C 800 800 o o C CPyroxene Chemistry Pyroxene Chemistry “Non “Non- -quad” pyroxenes quad” pyroxenes Jadeite Jadeite NaAlSi NaAlSi 2 2 O O 6 6 Ca(Mg,Fe)Si Ca(Mg,Fe)Si 2 2 O O 6 6 Aegirine Aegirine NaFe NaFe 3+ 3+ Si Si 2 2 O O 6 6 Diopside Diopside- -Hedenbergite Hedenbergite Ca Ca- -Tschermack’s Tschermack’s molecule molecule CaAl2SiO CaAl2SiO 6 6 Ca / (Ca + Na) Ca / (Ca + Na) 0.2 0.2 0.8 0.8 Omphacite aegirine- augite Augite Augite Spodumene: Spodumene: LiAlSi LiAlSi 2 2 O O 6 6Pyroxenoids Pyroxenoids “Ideal” pyroxene chains with “Ideal” pyroxene chains with 5.2 A repeat (2 tetrahedra) 5.2 A repeat (2 tetrahedra) become distorted as other become distorted as other cations occupy VI sites cations occupy VI sites Wollastonite Wollastonite (Ca (Ca ? ? M1) M1) ? ? 3 3- -tet repeat tet repeat Rhodonite Rhodonite MnSiO MnSiO 3 3 ? ? 5 5- -tet repeat tet repeat Pyroxmangite Pyroxmangite (Mn, Fe)SiO (Mn, Fe)SiO 3 3 ? ? 7 7- -tet repeat tet repeat Pyroxene Pyroxene 2 2- -tet repeat tet repeat 7.1 A 12.5 A 17.4 A 5.2 AInosilicates: double chains Inosilicates: double chains- - amphiboles amphiboles Tremolite (001) view blue = Si purple = M1 rose = M2 gray = M3 (all Mg) Tremolite (001) view blue = Si purple = M1 rose = M2 gray = M3 (all Mg) yellow = M4 (Ca) yellow = M4 (Ca) Tremolite: Tremolite: Ca Ca 2 2 Mg Mg 5 5 [Si [Si 8 8 O O 22 22 ] (OH) ] (OH) 2 2 b b a sin a sin ? ?Inosilicates: double chains Inosilicates: double chains- - amphiboles amphiboles Hornblende: Hornblende: (Ca, Na) (Ca, Na) 2 2- -3 3 (Mg, Fe, Al) (Mg, Fe, Al) 5 5 [(Si,Al) [(Si,Al) 8 8 O O 22 22 ] (OH) ] (OH) 2 2 b b a sin a sin ? ? Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) little turquoise ball = H little turquoise ball = HInosilicates: double chains Inosilicates: double chains- - amphiboles amphiboles Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 light blue = M3 (all Mg, Fe) light blue = M3 (all Mg, Fe) Hornblende: Hornblende: (Ca, Na) (Ca, Na) 2 2- -3 3 (Mg, Fe, (Mg, Fe, Al) Al) 5 5 [(Si,Al) [(Si,Al) 8 8 O O 22 22 ] ] (OH) (OH) 2 2 Same I Same I- -beam beam architecture, but architecture, but the I the I- -beams are beams are fatter (double fatter (double chains) chains)Inosilicates: double chains Inosilicates: double chains- - amphiboles amphiboles b b a sin a sin ? ? ( + ) ( + ) ( + ) ( + ) ( + ) ( + ) ( + ) ( + ) ( + ) ( + ) Same I Same I- -beam beam architecture, but architecture, but the I the I- -beams are beams are fatter (double fatter (double chains) chains) All are (+) on All are (+) on clinoamphiboles clinoamphiboles and alternate in and alternate in orthoamphiboles orthoamphiboles Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) little turquoise ball = H little turquoise ball = H Hornblende: Hornblende: (Ca, Na) (Ca, Na) 2 2- -3 3 (Mg, Fe, (Mg, Fe, Al) Al) 5 5 [(Si,Al) [(Si,Al) 8 8 O O 22 22 ] ] (OH) (OH) 2 2Inosilicates: double chains Inosilicates: double chains- - amphiboles amphiboles Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) little turquoise ball = H little turquoise ball = H Hornblende: Hornblende: (Ca, Na) (Ca, Na) 2 2- -3 3 (Mg, Fe, Al) (Mg, Fe, Al) 5 5 [(Si,Al) [(Si,Al) 8 8 O O 22 22 ] (OH) ] (OH) 2 2 M1 M1- -M3 are small sites M3 are small sites M4 is larger (Ca) M4 is larger (Ca) A A- -site is really big site is really big Variety of sites Variety of sites ? ? great chemical range great chemical rangeInosilicates: double chains Inosilicates: double chains- - amphiboles amphiboles Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 Hornblende (001) view dark blue = Si, Al purple = M1 rose = M2 light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) light blue = M3 (all Mg, Fe) yellow ball = M4 (Ca) purple ball = A (Na) little turquoise ball = H little turquoise ball = H Hornblende: Hornblende: (Ca, Na) (Ca, Na) 2 2- -3 3 (Mg, Fe, Al) (Mg, Fe, Al) 5 5 [(Si,Al) [(Si,Al) 8 8 O O 22 22 ] (OH) ] (OH) 2 2 (OH) is in center of (OH) is in center of tetrahedral ring where O tetrahedral ring where O is a part of M1 and M3 is a part of M1 and M3 octahedra octahedra (OH) (OH)See handout for more information See handout for more information General formula: General formula: W W 0 0- -1 1 X X 2 2 Y Y 5 5 [Z [Z 8 8 O O 22 22 ] (OH, F, Cl) ] (OH, F, Cl) 2 2 W = Na K W = Na K X = Ca Na Mg Fe X = Ca Na Mg Fe 2+ 2+ (Mn Li) (Mn Li) Y = Mg Fe Y = Mg Fe 2+ 2+ Mn Al Fe Mn Al Fe 3+ 3+ Ti Ti Z = Si Al Z = Si Al Again, the great variety of sites and sizes Again, the great variety of sites and sizes ? ? a great chemical range, and a great chemical range, and hence a broad stability range hence a broad stability range The The hydrous hydrous nature implies an upper temperature stability limit nature implies an upper temperature stability limit Amphibole Chemistry Amphibole ChemistryCa Ca- -Mg Mg- -Fe Amphibole “quadrilateral” (good analogy with pyroxenes) Fe Amphibole “quadrilateral” (good analogy with pyroxenes) Amphibole Chemistry Amphibole Chemistry Al and Na tend to stabilize the orthorhombic form in low Al and Na tend to stabilize the orthorhombic form in low- -Ca amphiboles, so anthophyllite Ca amphiboles, so anthophyllite ? ? gedrite orthorhombic series extends to Fe gedrite orthorhombic series extends to Fe- -rich gedrite in more Na rich gedrite in more Na- -Al Al- -rich compositions rich compositions Tremolite Tremolite Ca Ca 2 2 Mg Mg 5 5 Si Si 8 8 O O 22 22 (OH) (OH) 2 2 Ferroactinolite Ferroactinolite Ca Ca 2 2 Fe Fe 5 5 Si Si 8 8 O O 22 22 (OH) (OH) 2 2 Anthophyllite Anthophyllite Mg Mg 7 7 Si Si 8 8 O O 22 22 (OH) (OH) 2 2 Fe Fe 7 7 Si Si 8 8 O O 22 22 (OH) (OH) 2 2 Actinolite Cummingtonite-grunerite Orthoamphiboles Orthoamphiboles Clinoamphiboles ClinoamphibolesHornblende has Al in the tetrahedral site Hornblende has Al in the tetrahedral site Geologists traditionally use the term “hornblende” as a catch Geologists traditionally use the term “hornblende” as a catch- -all term for practically all term for practically any dark amphibole. Now the common use of the microprobe has petrologists any dark amphibole. Now the common use of the microprobe has petrologists casting “hornblende” into end casting “hornblende” into end- -member compositions and naming amphiboles member compositions and naming amphiboles after a well after a well- -represented end represented end- -member. member. Sodic amphiboles Sodic amphiboles Glaucophane: Na Glaucophane: Na 2 2 Mg Mg 3 3 Al Al 2 2 [Si [Si 8 8 O O 22 22 ] (OH) ] (OH) 2 2 Riebeckite: Na Riebeckite: Na 2 2 Fe Fe 2+ 2+ 3 3 Fe Fe 3+ 3+ 2 2 [Si [Si 8 8 O O 22 22 ] (OH) ] (OH) 2 2 Sodic amphiboles are commonly blue, and often called “blue amphiboles” Sodic amphiboles are commonly blue, and often called “blue amphiboles” Amphibole Chemistry Amphibole ChemistryTremolite (Ca Tremolite (Ca- -Mg) occurs in meta Mg) occurs in meta- -carbonates carbonates Actinolite occurs in low Actinolite occurs in low- -grade metamorphosed basic igneous rocks grade metamorphosed basic igneous rocks Orthoamphiboles and cummingtonite Orthoamphiboles and cummingtonite- -grunerite (all Ca grunerite (all Ca- -free, Mg free, Mg- -Fe Fe- -rich rich amphiboles) are metamorphic and occur in meta amphiboles) are metamorphic and occur in meta- -ultrabasic rocks and some ultrabasic rocks and some meta meta- -sediments. The Fe sediments. The Fe- -rich grunerite occurs in meta rich grunerite occurs in meta- -ironstones ironstones The complex solid solution called hornblende occurs in a broad variety of both The complex solid solution called hornblende occurs in a broad variety of both igenous and metamorphic rocks igenous and metamorphic rocks Sodic amphiboles are predominantly metamorphic where they are Sodic amphiboles are predominantly metamorphic where they are characteristic of high P/T subduction characteristic of high P/T subduction- -zone metamorphism (commonly called zone metamorphism (commonly called “blueschist” in reference to the predominant blue sodic amphiboles “blueschist” in reference to the predominant blue sodic amphiboles Riebeckite occurs commonly in sodic granitoid rocks Riebeckite occurs commonly in sodic granitoid rocks Amphibole Occurrences Amphibole OccurrencesInosilicates Inosilicates Pyroxenes and amphiboles are very similar: Pyroxenes and amphiboles are very similar: ? ? Both have chains of SiO Both have chains of SiO 4 4 tetrahedra tetrahedra ? ? The chains are connected into stylized I The chains are connected into stylized I- -beams by M octahedra beams by M octahedra ? ? High High- -Ca monoclinic forms have all the T Ca monoclinic forms have all the T- -O O- -T offsets in the same direction T offsets in the same direction ? ? Low Low- -Ca orthorhombic forms have alternating (+) and ( Ca orthorhombic forms have alternating (+) and (- -) offsets ) offsets + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - + + + + + + a a a a + + + + + + + + + + + + + + + + + + + + + + + + - - - - - - - - - - - - Clinopyroxene Clinopyroxene Orthopyroxene Orthopyroxene Orthoamphibole Orthoamphibole Clinoamphibole ClinoamphiboleInosilicates Inosilicates Cleavage angles can be interpreted in terms of weak bonds in M2 sites Cleavage angles can be interpreted in terms of weak bonds in M2 sites (around I (around I- -beams instead of through them) beams instead of through them) Narrow single Narrow single- -chain I chain I- -beams beams ? ? 90 90 o o cleavages in pyroxenes while wider double cleavages in pyroxenes while wider double- - chain I chain I- -beams beams ? ? 60 60- -120 120 o o cleavages in amphiboles cleavages in amphiboles pyroxene pyroxene amphibole amphibole a a b bPhyllosilicates Phyllosilicates Talc: Talc: Mg Mg 3 3 [Si [Si 4 4 O O 10 10 ] (OH) ] (OH) 2 2 T T- -layer layer - - tri triocathedral (Mg ocathedral (Mg 2+ 2+ ) layer ) layer - - T T- -layer layer T T O O T T - - T T O O T T - - T T O O T T vdw vdw vdw vdw weak van der Waals bonds between T weak van der Waals bonds between T - - O O - - T groups T groups Yellow = (OH) Yellow = (OH)Phyllosilicates Phyllosilicates Muscovite: Muscovite: K K Al Al 2 2 [Si [Si 3 3 Al AlO O 10 10 ] (OH) ] (OH) 2 2 (coupled K (coupled K - - Al Al IV IV ) ) T T- -layer layer - - di diocathedral (Al ocathedral (Al 3+ 3+ ) layer ) layer - - T T- -layer layer - - K K T T O O T T K K T T O O T T K K T T O O T T K between T K between T - - O O - - T groups is stronger than vdw T groups is stronger than vdwPhyllosilicates Phyllosilicates Phlogopite: Phlogopite: K Mg K Mg 3 3 [Si [Si 3 3 AlO AlO 10 10 ] (OH) ] (OH) 2 2 T T- -layer layer - - tri triocathedral (Mg ocathedral (Mg 2+ 2+ ) layer ) layer - - T T- -layer layer - - K K T T O O T T K K T T O O T T K K T T O O T T K between T K between T - - O O - - T groups is stronger than vdw T groups is stronger than vdwA Summary of A Summary of Phyllosilicate Structures Phyllosilicate Structures Phyllosilicates Phyllosilicates Fig 13.84 Klein and Hurlbut Manual of Mineralogy, © John Wiley & SonsWhy are there single Why are there single- -chain chain- -, double , double- -chain chain- -, and sheet , and sheet- -polymer types, polymer types, and not triple chains, quadruple chains, etc?? and not triple chains, quadruple chains, etc?? “Biopyriboles” “Biopyriboles”It turns out that there are some It turns out that there are some intermediate types, predicted by intermediate types, predicted by J.B. Thompson and discovered in J.B. Thompson and discovered in 1977 Veblen, Buseck, and 1977 Veblen, Buseck, and Burnham Burnham Cover of Science: anthophyllite Cover of Science: anthophyllite (yellow) reacted to form chesterite (yellow) reacted to form chesterite (blue & green) and jimthompsonite (blue & green) and jimthompsonite (red) (red) Streaked areas are highly Streaked areas are highly disordered disordered “Biopyriboles” “Biopyriboles” Cover of Science, October 28, 1977 © AAASHRTEM image of anthophyllite (left) with typical double HRTEM image of anthophyllite (left) with typical double- -chain width chain width Jimthompsonite (center) has triple Jimthompsonite (center) has triple- -chains chains Chesterite is an ordered alternation of double Chesterite is an ordered alternation of double- - and triple and triple- -chains chains anthophyllite anthophyllite jimthompsonite jimthompsonite chesterite chesterite Fig. 6, Veblen et al (1977) Science 198 © AAASDisordered structures show 4 Disordered structures show 4- -chain widths and even a 7 chain widths and even a 7- -chain width chain width Obscures the distinction between pyroxenes, amphiboles, and micas Obscures the distinction between pyroxenes, amphiboles, and micas (hence the term biopyriboles: (hence the term biopyriboles: bio biotite tite- -pyr pyroxene oxene- -amph amphibole ibole) ) “Biopyriboles” “Biopyriboles” Fig. 7, Veblen et al (1977) Science 198 © AAAS