Feldspar Group

Feldspar GroupFeldspar Group Most abundant mineral in Most abundant mineral in

the crust the crust 6 of 7 most 6 of 7 most common elementscommon elements

Defined through 3 end-Defined through 3 end-members members Albite (Na), Anorthite (Ca), Albite (Na), Anorthite (Ca),

Orthoclase (K)Orthoclase (K) Comprised of 2 series:Comprised of 2 series:

Albite-anorthite (Na-Ca)Albite-anorthite (Na-Ca) Albite-orthoclase (Na-K)Albite-orthoclase (Na-K)

TectosilicatesTectosilicatesFeldsparsFeldspars

Albite: Albite: NaNaAlAlSiSi33OO88

Substitute two Substitute two AlAl3+3+ for Si for Si4+4+ allows Caallows Ca2+2+ to be to be addedaddedAlbite-AnorthiteAlbite-Anorthite

Substitute AlSubstitute Al3+3+ for Sifor Si4+4+ allows allows NaNa++ or K or K++ to be to be addedaddedAlbite-OrthoclaseAlbite-Orthoclase

Feldspar Group – Albite-Anorthite seriesFeldspar Group – Albite-Anorthite series Complete solid solution Complete solid solution Plagioclase FeldsparsPlagioclase Feldspars 6 minerals6 minerals

Albite (Na)Albite (Na) OligoclaseOligoclase AndesineAndesine LabradoriteLabradorite BytowniteBytownite Anorthite (Ca)Anorthite (Ca)

Albite-Anorthite double dutyAlbite-Anorthite double duty End-members (Pure Na or Ca)End-members (Pure Na or Ca) Minerals 90-99.99% Na or CaMinerals 90-99.99% Na or Ca

Notation:Notation: AnAnxxAbAbyy An An2020AbAb8080=Oligoclase=Oligoclase

Feldspar Group – Albite-Anorthite seriesFeldspar Group – Albite-Anorthite series Optical techniques to Optical techniques to

distinguish between distinguish between plagioclase feldspars:plagioclase feldspars: Michel-Levy Method – uses Michel-Levy Method – uses

extinction angles of extinction angles of twinned forms to determine twinned forms to determine An-Ab contentAn-Ab content

Combined Carlsbad-Albite Combined Carlsbad-Albite Method Method uses Michel- uses Michel-Levy technique for both Levy technique for both sides of a twin formsides of a twin form

Feldspar Group – Albite-Orthoclase seriesFeldspar Group – Albite-Orthoclase series

High – T mineralsHigh – T minerals SanidineSanidine AnorthoclaseAnorthoclase MonalbiteMonalbite High AlbiteHigh Albite

Low Temperature Low Temperature exsolution at solvusexsolution at solvus Chicken soup Chicken soup

separationseparation Forms 2 minerals, in igneous Forms 2 minerals, in igneous

rocks these are typically rocks these are typically intergrowths, or exsolution intergrowths, or exsolution lamellae – perthitic texturelamellae – perthitic texture

Miscibility Gapmicrocline

orthoclase

sanidine

anorthoclasemonalbite

high albite

low albite

intermediate albite

OrthoclaseKAlSi3O8

AlbiteNaAlSi3O8

% NaAlSi3O8

Tem

pera

ture

(Te

mpe

ratu

re ( º

C)

ºC)

300300

900900

700700

500500

11001100

1010 9090707050503030

Several minerals – Several minerals – Alkali FeldsparsAlkali Feldspars

Alkali Feldspar ExsolutionAlkali Feldspar Exsolution

Melt cools past solvus Melt cools past solvus (line defining (line defining miscibility gap)miscibility gap)

Anorthoclase, that had Anorthoclase, that had formed (through formed (through liquidus/solidus) liquidus/solidus) separates (if cooling is separates (if cooling is slow enough) to form slow enough) to form orthoclase orthoclase andand low low albitealbite

In hand sample – In hand sample – schiller effect schiller effect play play of colors caused by of colors caused by lamellaelamellae

Miscibility Gapmicrocline

orthoclase

sanidine

anorthoclasemonalbite

high albite

low albite

intermediate albite

OrthoclaseKAlSi3O8

AlbiteNaAlSi3O8

% NaAlSi3O8

Tem

pera

ture

(Te

mpe

ratu

re ( º

C)

ºC)

300300

900900

700700

500500

11001100

1010 9090707050503030

Liquid

Alkali Feldspar lamellaeAlkali Feldspar lamellae

Feldspathoid GroupFeldspathoid Group Very similar to Very similar to

feldspars and zeolitesfeldspars and zeolites Include Nepheline, Include Nepheline,

Analcime, and LeuciteAnalcime, and Leucite Also framework Also framework

silicates, but with silicates, but with another Al substitution another Al substitution for Sifor Si

Only occur in Only occur in undersaturated rocks undersaturated rocks (no free Quartz, Si-(no free Quartz, Si-poor) because they poor) because they react with SiOreact with SiO22 to form to form feldsparsfeldspars

Olivine (001) view blue = M1 yellow = M2Olivine (001) view blue = M1 yellow = M2

M1 in rows M1 in rows and share and share edgesedges

M2 form M2 form layers in a-c layers in a-c that share that share corners corners

Some M2 and Some M2 and M1 share M1 share edgesedges

bb

aa

Nesosilicates: independent SiONesosilicates: independent SiO44 tetrahedra tetrahedra

Olivine – complete solid solution Olivine – complete solid solution Forsterite-Fayalite Forsterite-Fayalite Fo FoxxFaFayy

Fayalite – Fe end-member Fayalite – Fe end-member Forsterite – Mg end-memberForsterite – Mg end-member

Olivine Occurrences:Olivine Occurrences: Principally in mafic and ultramafic igneous and meta-igneous Principally in mafic and ultramafic igneous and meta-igneous

rocksrocks Fayalite in meta-ironstones and in some alkalic granitoidsFayalite in meta-ironstones and in some alkalic granitoids Forsterite in some siliceous dolomitic marblesForsterite in some siliceous dolomitic marbles

Monticellite CaMgSiOMonticellite CaMgSiO44 Ca Ca M2 (larger ion, larger site) M2 (larger ion, larger site)High grade metamorphic siliceous carbonatesHigh grade metamorphic siliceous carbonates

Distinguishing Forsterite-FayaliteDistinguishing Forsterite-Fayalite

Petrographic MicroscopePetrographic Microscope Index of refraction Index of refraction careful of zoning!! careful of zoning!! 2V different in different composition ranges2V different in different composition ranges Pleochroism/ color slightly differentPleochroism/ color slightly different

Spectroscopic techniques – many ways to Spectroscopic techniques – many ways to determine Fe vs. Mgdetermine Fe vs. Mg

Same space group (Pbnm), Orthorhombic, slight Same space group (Pbnm), Orthorhombic, slight differences in unit cell dimensions onlydifferences in unit cell dimensions only

Inosilicates: single chains- Inosilicates: single chains- pyroxenespyroxenes

Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)Diopside (001) view blue = Si purple = M1 (Mg) yellow = M2 (Ca)

Diopside: CaMg [SiDiopside: CaMg [Si22OO66]]

bb

a si

na

sin

Where are the Si-O-Si-O chains??Where are the Si-O-Si-O chains??

Inosilicates: single chains- pyroxenes Inosilicates: single chains- pyroxenes


bb

a si

na

sin



bb

a si

na

sin



bb

a si

na

sin



bb

a si

na

sin



bb

a si

na

sin



Perspective viewPerspective view



SiOSiO44 as polygons as polygons

(and larger area)(and larger area)IV slabIV slab

IV slabIV slab

IV slabIV slab

IV slabIV slab

VI slabVI slab

VI slabVI slab

VI slabVI slab

bb

a si

na

sin


M1 octahedronM1 octahedron





(+) type by convention(+) type by convention

(+)



This is a (-) typeThis is a (-) type

(-)


TT

M1M1

TT

Creates an “I-beam” Creates an “I-beam” like unit in the like unit in the

structure.structure.


TT

M1M1

TT

Creates an “I-beam” Creates an “I-beam” like unit in the like unit in the

structurestructure

(+)(+)

The pyroxene The pyroxene structure is then structure is then

composed of composed of alternating I-beamsalternating I-beams

Clinopyroxenes have Clinopyroxenes have all I-beams oriented all I-beams oriented the same: all are (+) the same: all are (+) in this orientation in this orientation

(+)(+)

(+)(+)(+)(+)

(+)(+)(+)(+)


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 chainstetrahedral chains

The pyroxene The pyroxene structure is then structure is then

composed of composed of alternation I-beamsalternation I-beams

Clinopyroxenes have Clinopyroxenes have all I-beams oriented all I-beams oriented the same: all are (+) the same: all are (+) in this orientation in this orientation

Orthopyroxenes have Orthopyroxenes have alternating (+) and (-) alternating (+) and (-)

orientationsorientations

(+)(+)

(+)(+)(+)(+)


(+)(+)(+)(+)

Tetrehedra and M1 Tetrehedra and M1 octahedra share octahedra share

tetrahedral apical tetrahedral apical oxygen atoms oxygen atoms


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 effectsimilar effect

The result is a The result is a monoclinicmonoclinic unit cell, unit cell, hence hence clinopyroxenesclinopyroxenes


cc

aa

(+) M1(+) M1

(+) M2(+) M2

(+) M2(+) M2

OrthopyroxenesOrthopyroxenes have have alternating (+) and (-) alternating (+) and (-)

I-beams I-beams

the offsets thus the offsets thus compensate and result compensate and result in an in an orthorhombicorthorhombic

unit cellunit cell


cc

aa

(+) M1(+) M1

(-) M1(-) M1

(-) M2(-) M2

(+) M2(+) M2

Pyroxene ChemistryPyroxene Chemistry

The general pyroxene formula: The general pyroxene formula: WW1-P1-P (X,Y) (X,Y)1+P1+P Z Z22OO66

WhereWhere W = W = CaCa Na Na X = X = Mg FeMg Fe2+2+ Mn Ni Li Mn Ni Li Y = Al FeY = Al Fe3+3+ Cr Ti Cr Ti Z = Z = SiSi Al Al

Anhydrous Anhydrous so high-temperature or dry conditions so high-temperature or dry conditions favor pyroxenes over amphibolesfavor pyroxenes over amphiboles

Pyroxene ChemistryPyroxene ChemistryThe pyroxene quadrilateral and opx-cpx solvusThe pyroxene quadrilateral and opx-cpx solvus

Coexisting opx + cpx in many rocks (pigeonite only in volcanics)Coexisting opx + cpx in many rocks (pigeonite only in volcanics)

DiopsideDiopsideCaMgSiCaMgSi22OO66

HedenbergiteHedenbergite CaFeSiCaFeSi22OO66

Wollastonite CaWollastonite Ca22SiSi22OO66

EnstatiteEnstatiteMgMg22SiSi22OO66

FerrosiliteFerrosiliteFeFe22SiSi22OO66

orthopyroxenes

clinopyroxenes

pigeonite

•OrthopyroxenesOrthopyroxenes – solid soln – solid soln between Enstatite-Ferrosilitebetween Enstatite-Ferrosilite•Clinopyroxenes – solid soln – solid soln between Diopside-Hedenbergitebetween Diopside-Hedenbergite

Joins – lines between end Joins – lines between end members – limited mixing members – limited mixing away from joinaway from join

Orthopyroxene - ClinopyroxeneOrthopyroxene - ClinopyroxeneOPX and CPX have different crystal structures OPX and CPX have different crystal structures

– results in a complex solvus between them– results in a complex solvus between themCoexisting opx + cpx in many rocks (pigeonite only in volcanics)Coexisting opx + cpx in many rocks (pigeonite only in volcanics)

DiopsideDiopsideCaMgSiCaMgSi22OO66

HedenbergiteHedenbergite CaFeSiCaFeSi22OO66

Wollastonite CaWollastonite Ca22SiSi22OO66

EnstatiteEnstatiteMgMg22SiSi22OO66

FerrosiliteFerrosiliteFeFe22SiSi22OO66

orthopyroxenes

clinopyroxenes

pigeonite

(Mg,Fe)(Mg,Fe)22SiSi22OO66 Ca(Mg,Fe)SiCa(Mg,Fe)Si22OO66

pigeonite clinopyroxenes

orthopyroxenes

SolvusSolvus

12001200ooCC

10001000ooCC

800800ooCC

OPXOPX CPXCPX

CPXCPX

OPXOPX

Orthopyroxene – ClinopyroxeneOrthopyroxene – Clinopyroxenesolvus T dependencesolvus T dependence

Complex solvus – the ‘stability’ of a particular mineral changes Complex solvus – the ‘stability’ of a particular mineral changes with T. A different mineral’s ‘stability’ may change with T with T. A different mineral’s ‘stability’ may change with T differently…differently…

OPX-CPX exsolution lamellae OPX-CPX exsolution lamellae Geothermometer… Geothermometer…

MiscibilityGap

FsFsEnEn

DiDi HdHd

FsFsEnEn

DiDi HdHd

OPXOPXOPXOPX

CPXCPX CPXCPX

pigeonite

augite

orthopyroxene

Pigeonite + orthopyroxene

orthopyroxene

Subcalcic augite

pigeonite

augite

MiscibilityGap

800800ºCºC 12001200ºCºC

PyroxenoidsPyroxenoids““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 sitescations occupy VI sites

WollastoniteWollastonite (Ca (Ca M1) M1) 3-tet repeat3-tet repeat

RhodoniteRhodoniteMnSiOMnSiO33

5-tet repeat5-tet repeat

PyroxmangitePyroxmangite (Mn, Fe)SiO(Mn, Fe)SiO33

7-tet repeat7-tet repeat

PyroxenePyroxene2-tet repeat2-tet repeat

7.1 A12.5 A

17.4 A

5.2 A

Inosilicates: double chains- Inosilicates: double chains- amphibolesamphiboles

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:CaCa22MgMg55 [Si [Si88OO2222] (OH)] (OH)22

bb

a si

na

sin


Hornblende:Hornblende:(Ca, Na)(Ca, Na)2-3 2-3 (Mg, Fe, Al) (Mg, Fe, Al)55

[(Si,Al)[(Si,Al)88OO2222] (OH)] (OH)22

bb

a si

na

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 = Hlittle turquoise ball = H


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)2-3 2-3 (Mg, Fe, (Mg, Fe,

Al)Al)55 [(Si,Al) [(Si,Al)88OO2222] (OH)] (OH)22

Same I-beam Same I-beam architecture, but architecture, but the I-beams are the I-beams are fatter (double fatter (double

chains)chains)

Inosilicates: double chains- Inosilicates: double chains- amphibolesamphiboles bb

a si

na

sin

(+)(+) (+)(+)

(+)(+)

(+)(+)

(+)(+)

Same I-beam Same I-beam architecture, but architecture, but the I-beams are the I-beams are fatter (double fatter (double

chains)chains)

All are (+) on All are (+) on clinoamphiboles clinoamphiboles and alternate in and alternate in

orthoamphibolesorthoamphiboles



Hornblende:Hornblende:(Ca, Na)(Ca, Na)2-3 2-3 (Mg, Fe, (Mg, Fe,

Al)Al)55 [(Si,Al) [(Si,Al)88OO2222] (OH)] (OH)22





[(Si,Al)[(Si,Al)88OO2222] (OH)] (OH)22

M1-M3 are small sitesM1-M3 are small sites

M4 is larger (Ca)M4 is larger (Ca)

A-site is really bigA-site is really big

Variety of sites Variety of sites great chemical rangegreat chemical range





[(Si,Al)[(Si,Al)88OO2222] (OH)] (OH)22

(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

octahedraoctahedra

(OH)(OH)

See handout for more informationSee handout for more informationGeneral formula:General formula:

WW0-10-1 X X22 Y Y55 [Z [Z88OO2222] (OH, F, Cl)] (OH, F, Cl)22

W = Na KW = Na KX = Ca Na Mg FeX = Ca Na Mg Fe2+2+ (Mn Li) (Mn Li)Y = Mg FeY = Mg Fe2+2+ Mn Al Fe Mn Al Fe3+3+ Ti TiZ = Si AlZ = 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 rangehence a broad stability range

The The hydroushydrous nature implies an upper temperature stability limit nature implies an upper temperature stability limit

Amphibole ChemistryAmphibole Chemistry

Ca-Mg-Fe Amphibole “quadrilateral” (good analogy with pyroxenes)Ca-Mg-Fe Amphibole “quadrilateral” (good analogy with pyroxenes)


Al and Na tend to stabilize the orthorhombic form in low-Ca amphiboles, so anthophyllite Al and Na tend to stabilize the orthorhombic form in low-Ca amphiboles, so anthophyllite gedrite orthorhombic series extends to Fe-rich gedrite in more Na-Al-rich compositions gedrite orthorhombic series extends to Fe-rich gedrite in more Na-Al-rich compositions

TremoliteTremoliteCaCa22MgMg55SiSi88OO2222(OH)(OH)22

FerroactinoliteFerroactinoliteCaCa22FeFe55SiSi88OO2222(OH)(OH)22

AnthophylliteAnthophyllite

MgMg77SiSi88OO2222(OH)(OH)22FeFe77SiSi88OO2222(OH)(OH)22

Actinolite

Cummingtonite-grunerite

OrthoamphibolesOrthoamphiboles

ClinoamphibolesClinoamphiboles

Hornblende has Al in the tetrahedral siteHornblende has Al in the tetrahedral site

Geologists traditionally use the term “hornblende” as a catch-all term for practically Geologists traditionally use the term “hornblende” as a catch-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-member compositions and naming amphiboles casting “hornblende” into end-member compositions and naming amphiboles after a well-represented end-member.after a well-represented end-member.

Sodic amphiboles Sodic amphiboles

Glaucophane: NaGlaucophane: Na2 2 MgMg3 3 AlAl2 2 [Si[Si88OO2222] (OH)] (OH)22

Riebeckite: NaRiebeckite: Na2 2 FeFe2+2+3 3 FeFe3+3+

2 2 [Si[Si88OO2222] (OH)] (OH)22

Sodic amphiboles are commonly blue, and often called “blue amphiboles”Sodic amphiboles are commonly blue, and often called “blue amphiboles”


InosilicatesInosilicates

Pyroxenes and amphiboles are very similar:Pyroxenes and amphiboles are very similar: Both have chains of SiOBoth have chains of SiO44 tetrahedra tetrahedra The chains are connected into stylized I-beams by M octahedraThe chains are connected into stylized I-beams by M octahedra High-Ca monoclinic forms have all the T-O-T offsets in the same directionHigh-Ca monoclinic forms have all the T-O-T offsets in the same direction Low-Ca orthorhombic forms have alternating (+) and (-) offsetsLow-Ca orthorhombic forms have alternating (+) and (-) offsets

++++ ++

++++++

++++++ --

-- --

----

--

++++++

aa

aa

++++ ++

++++ ++

++++ ++

++++ ++

----

--

----

--

ClinopyroxeneClinopyroxene

OrthopyroxeneOrthopyroxene OrthoamphiboleOrthoamphibole

ClinoamphiboleClinoamphibole

InosilicatesInosilicates

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-beams instead of through them)(around I-beams instead of through them)

Narrow single-chain I-beams Narrow single-chain I-beams 90 90oo cleavages in pyroxenes while wider double- cleavages in pyroxenes while wider double-chain I-beams chain I-beams 60-120 60-120oo cleavages in amphiboles cleavages in amphiboles

pyroxenepyroxene amphiboleamphibole

aa

bb

TectosilicatesTectosilicates

Stishovite

Coesite

- quartz

- quartzLiquid

TridymiteCristobalite

600 1000 1400 1800 2200 2600

2

4

6

8

10P

ress

ure

(GP

a)

Temperature oC

After Swamy and Saxena (1994) J. Geophys. Res., 99, 11,787-11,794.


Low QuartzLow Quartz

001 Projection Crystal Class 32001 Projection Crystal Class 32

Stishovite

Coesite

- quartz

- quartzLiquid



High Quartz at 581High Quartz at 581ooCC

001 Projection Crystal Class 622001 Projection Crystal Class 622

Stishovite

Coesite

- quartz

- quartzLiquid



CristobaliteCristobalite

001 Projection Cubic Structure001 Projection Cubic Structure

Stishovite

Coesite

- quartz

- quartzLiquid



StishoviteStishovite

High pressure High pressure Si SiVIVI

Stishovite

Coesite

- quartz

- quartzLiquid



Low Quartz StishoviteLow Quartz Stishovite

SiSiIVIV Si SiVIVI

SiOSiO44 tetrahedra polymerized into 2-D sheets: [Si tetrahedra polymerized into 2-D sheets: [Si22OO55]]

Apical O’s are unpolymerized and are bonded to other constituentsApical O’s are unpolymerized and are bonded to other constituents

PhyllosilicatesPhyllosilicates

Tetrahedral 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


Octahedral layers can be understood by analogy with hydroxidesOctahedral layers can be understood by analogy with hydroxides


Brucite: Mg(OH)Brucite: Mg(OH)22

Layers of octahedral Mg in Layers of octahedral Mg in coordination with (OH)coordination with (OH)

Large spacing along Large spacing along cc due due to weak van der waals to weak van der waals bondsbonds

cc


Gibbsite: Al(OH)Gibbsite: Al(OH)33

Layers of octahedral Al in coordination with (OH)Layers of octahedral Al in coordination with (OH)

AlAl3+3+ means that means that only 2/3 of the VI sites may be occupiedonly 2/3 of the VI sites may be occupied for charge-balance reasons for charge-balance reasons

Brucite-type layers may be called Brucite-type layers may be called trioctahedraltrioctahedral and gibbsite-type and gibbsite-type dioctahedraldioctahedral

aa11

aa22


Muscovite:Muscovite: KK Al Al22 [Si [Si33AlAlOO1010] (OH)] (OH)2 2 (coupled K - Al(coupled K - AlIVIV))

T-layer - T-layer - didiocathedral (Alocathedral (Al3+3+) layer - T-layer - ) layer - T-layer - KK

T T O O T T KK T T O O T T KK T T O O TT

K between T - O - T groups is stronger than vdwK between T - O - T groups is stronger than vdw


Phlogopite:Phlogopite: K Mg K Mg33 [Si [Si33AlOAlO1010] (OH)] (OH)22

T-layer - T-layer - tritriocathedral (Mgocathedral (Mg2+2+) layer - T-layer - ) layer - T-layer - KK

T T O O T T KK T T O O T T KK T T O O TT

K between T - O - T groups is stronger than vdwK between T - O - T groups is stronger than vdw

Igneous MineralsIgneous Minerals Quartz, Feldspars (plagioclase and alkaline), Quartz, Feldspars (plagioclase and alkaline),

Olivines, Pyroxenes, AmphibolesOlivines, Pyroxenes, Amphiboles Accessory Minerals – mostly in small quantities or Accessory Minerals – mostly in small quantities or

in ‘special’ rocksin ‘special’ rocks Magnetite (FeMagnetite (Fe33OO44)) Ilmenite (FeTiOIlmenite (FeTiO33)) Apatite (CaApatite (Ca55(PO(PO44))33(OH,F,Cl)(OH,F,Cl) Zircon (ZrSiOZircon (ZrSiO44)) Sphene (a.k.a. Titanite) (CaTiSiOSphene (a.k.a. Titanite) (CaTiSiO55)) Pyrite (FeSPyrite (FeS22)) Fluorite (CaFFluorite (CaF22))

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Feldspar Group