CHAPTER 7: NON-SILICATES MINERALS Sarah Lambart

� Part 1: Crystal growth

� Environments: Vapor, fluid or solid

� 2 processes: Nucleation and Transport (+ appropriate P-T conditions)

� 3 possible states: stable, metastable and unstable

� Condition for crystallization: ΔGf < 0

� Nucleation:

� ΔG* = nucleation energy

� r* = critical radius

� Homogene vs. heterogene

RECAP CHAPT. 6

� Part 1: Crystal growth

� Crystallization: minimize the surface/volume ration

� Three type of surfaces: K, S, F

� Screw dislocation: promotes growth by creating new S sites

� Growth rates: faster along long crystallographic directions ⇒ faces more developed along short crystallographic directions

� Dendritic crystals: fast crystallization limited by transport

� Zoned crystals: solid solutions reflecting a change of environment

� Oswald ripening: pure thermodynamic process (constant P, T, X) to minimize the surface/volume ratio ⇔ minimize energy

RECAP CHAPT. 6

� Part 2: XRD – powder method

� Identification of minerals:

� Pros: inexpensive, fast, widely available

� Cons: destructive, relatively high limit of detection

� X-rays: electromagnetic radiation - λ= 0.02-100 * 10-10 m ~ atom size ⇒ penetrate matter more easily than visible light

� Generation of X-ray: X-ray tube: bombardment of an anode with electron ⇒ perturbation electronic

� X-ray penetrating a crystal: follow the Bragg law: nλ = 2d sinθ: b λ and θ known ⇒ determination of d (spacing between the atomic planes)

� Use of a powder: determination of the spectra for 0-90° ⇒ comparison with the spectra collection.

RECAP CHAPT. 6

� Part 1: Native element

� Part 2: Sulfides and related minerals

� Part 3 : Oxides, Hydroxides and Halides

� Part 4: Carbonates, Sulfates and Phosphates

CONTENT CHAPT. 7 (3 LECTURES)

MINERAL CLASSIFICATION �  Principally by dominant anion or anionic group

�  Secondarily by internal mineral structure

Native Element Sulfides (S2-) Oxides (O2-) Hydroxides (OH-) Halides (Cl-, F-, Br-, I-) Carbonates (CO3

2-) & nitrates Sulfates (SO4

2-) Phosphates (PO4

3-) & arsenates, vanadates Borates (BO3

2-)

Silicates (SiO44-)

Nesosilicates or orthosilicates Sorosilicates Cyclosilicates

Inosilicates or chain silic. Phyllosilicates or sheet silic.

Tectosilicates or framework silic.

PART 1: NATIVE ELEMENTS Chapter 20 in Bulakh

Chapter 20 in Nesse

NATIVE ELEMENTS

� Rare (0.0002 wt.% of Earth’s crust), simple, form under unusual conditions

� Structure: close-packing arrangement � Native element classification:

� Metals: � Gold group: Gold (Au), Silver (Ag), Copper (Cu), Lead (Pb) �  Platinum group: Platinum (Pt), Palladium (Pa), Osmium (Os),

Iridium (Ir) �  Iron group: Iron (Fe), Fe-nickel (Fe-Ni), Mercury (Hg)

� Semi-metals – Arsenic (As), Bismuth (Bi), Antimony (Sb) � Non-metals – Sulfur (S), Diamond (C), Graphite(C)

METALS �  3 groups:

�  Gold group: Gold (Au), Silver (Ag), Copper (Cu), Lead (Pb) Properties: ductile, good conductors, opaque � Solid-solutions: Au-Ag, Au-Cu (+ Au-Pa, Au-Hg); Cu-Zn (brass) � Melting points: Au: 1064°C, Ag: 961.8°C, Cu:1085°C

�  Platinum group: Platinum (Pt), Palladium (Pa), iridium-Osmium (Os,Ir), platinum-Iridium (Pt,Ir) � Melting point: Pt: 1768°C; Pa: 1555°C � Solid solutions: Pt-Fe (experimental issue)

�  Iron group: Iron (Fe), Fe-nickel (Fe-Ni), Mercury (Hg), Zinc (Zn)

� Crystal structure: ffc except Hg (rhomb.), Zinc (hcp) � Opaque, ductile, high density, metallic luster, good conductors heat

+ electricity

METALS: OCCURRENCES AND FORMATION

� Gold – Hydrothermal fluids related to magmatism; commonly occurs in veins of quartz and pyrite; may form detrital grains to produce placer deposits; Rarely occurs alloyed with other elements.

METALS: OCCURRENCES AND FORMATION

� Gold – Hydrothermal fluids related to magmatism; commonly occurs in veins of quartz and pyrite; may form detrital grains to produce placer deposits; Rarely occurs alloyed with other elements.

� Silver– Hydrothermal ore deposits rich in sulfides, arsenides, and bismuthides; also commonly associated native copper.

METALS: OCCURRENCES AND FORMATION

� Copper- Most commonly found associated with mafic volcanic rock, where it is formed by reaction between Cu-bearing solution and Fe-bearing minerals; most abundant occurrence is the native copper deposits of the Keweenawan Peninsula of Upper Michigan where it occurs in lava flows and interflow conglomerates. Can also be found in sedimentary rock, formed by the same process. Or in oxidized zones of Cu-bearing hydrothermal sulfide deposit

Copper Harbor conglomerate

METALS: OCCURRENCES AND FORMATION

� Copper- Most commonly found associated with mafic volcanic rock, where it is formed by reaction between Cu-bearing solution and Fe-bearing minerals; most abundant occurrence is the native copper deposits of the Keweenawan Peninsula of Upper Michigan where it occurs in lava flows and interflow conglomerates. Can also be found in sedimentary rock, formed by the same process. Or in oxidized zones of Cu-bearing hydrothermal sulfide deposit

� Platinum – Occurs as primary deposits in mafic intrusions or in ultramafic rocks – peridotite complexes and ophiolites - (required low fugacity – possible in the Earth mantle) and as secondary placer deposits.

METALS: CURRENT PRICES

Au: 1165 Ag: 16 Pt: 1000 Cu: 2.40 Pa: 690

Ir: 520 Pb: 0.79 Zn: 0.78 Ni: 4.70 Fe: 56

$USD/otz otz = troy ounce = 31.1034768 g

SEMIMETALS

� Arsenic (As), Bismuth (Bi), Antimony (Sb) � Crystal structure: trigonal � Luster: metallic; Opaque � Occurrences: hydrothermal sulfides deposits

NON METALS

Diamond (C), graphite (C), sulfur (S)

NON METALS: PHYSICAL PROPERTIES

Diamond (C) Graphite (C) Sulfur (S) � Unit cell: Cubic hexagonal orthorhombic � Form: Octahedron platy hexag. Pyramidal or

or globular tabular � Luster : Adamantine dull metallic Resinous or

or earthy greasy

� Color/streak: colorless/white Black/black Yellow/white � Relief: +++ +++

NON METALS: STRUCTURE

� Diamond

� Each carbon form a tetrahedral bon with four other carbon atoms.

NON METALS: STRUCTURE

� Graphite

� Sheets of carbon atoms parallel to (001)

NON METALS: STRUCTURE

� Sulfur

� Rings of eight covalently bonded S atoms forming S8 molecules, stacked on top of each other, some parallel to (110) and other to (001)

Projection along (110)

NON METALS: OCCURRENCES

�  Diamond: �  Form at mantle depths (650 km) (the

most common) � Deposit: diatremes of kimberlites (very fluid

ultramafic lava)

�  Form in eclogite and schist at great crustal depths (extremely small diamonds)

�  Form during meteorite impact (in both meteorite and rock underlying): Shock pressure > 8 GPa (~260-280 km)

�  Metastable in reduced conditions ≠ Unstable in oxidized conditions

Credits: Raj Dasgupta, Rice University

NON METALS: OCCURRENCES

� Graphite:

�  Common in pelitic metamorphic rocks (metamorphosed shales: phyllite, slate, schist)

�  In marble (metamorphosed carbonate) and skarn (calc-silicate rock formed by the contact of a carbonate rock with a magmatic intrusion) deposits

�  In metamorphosed coal beds �  Rare in igneous rocks

NON METALS: OCCURRENCES

� Sulfur: �  Around fumaroles, volcanic vent, hot spring deposits: recent or active volcanism �  Largest concentrations: associated with salt domes – marine evaporite deposits

PART 2: SULFIDES AND RELATED MINERALS Chapter 24 in Wenk and Bulakh

Chapter 19 in Nesse

DEFINITION

� Large group of minerals 500-600 � Great economic value: principal ore of metals � Definition and classification

� MpXr: - M is a metal or semimetal (Fe, Zn, Cu, Pb, As, Sb, Bi) - X can be: + S (sulfides) + As (Arsenides) + S + As (sulfarsenides) + Te (tellurides)

Name Chemical formula

Chalcoite Cu2S

Galena PbS

Pyrrhoite Fe1-xS

Sphalarite ZnS or (Fe,Zn)S

Chalcopyrite CuFeS2

Pyrite & marcasite FeS2

Marcasite FeS2

Pentlandite (Fe, Ni)9S8

Cinnabar HgS

Arsenopyrite FeAsS

Nickeline NiAs

Sylvarite (Au,Ag, Te2)

Sulfides

Arsenides Tellurides

Sulfarsenides

COMMON SULFIDES AND RELATED MINERALS

STRUCTURE

� Sphalerite ZnS

� Zn: fcc � S: tetrahedral sites

PROPERTIES

� Galena PbS

� Form: cube � Color: dark gray � Luster: metallic � Structure:2 interconnected fcc

(as halite)

PROPERTIES

� Pyrite FeS2

� Form: cube � Color: pale brass yellow � Luster: metallic � Structure:

� Fe: fcc � S2: fcc

FORMATION � Hydrothermal deposit: vein mineralization

� Veins: - former fractures or fluid pathways filled by minerals - ⇐ deposit of hydrothermal solutions (i.e., hot water)

� Ingredients: Water (meteoric, magmatic, metamorphic or connate) + Heat (igneous intrusion, via burial, magma chamber)

� Temperature origin: - low: 50-150°C - intermediate: 150-400°C - high: 400-600°C

FORMATION

� Supergene process � Alteration: primary ore mineral may alter

to the surface to secondary (or supergene) minerals

Ex.: pyrite, chalcopyrite, sphalarite. ⇒ oxidation of metals into oxides, hydroxides, carbonates and sulfates

� Reprecipitation of water carrying dissolved metal ⇒ supergene enrichments

Fig. 19.3 in Nesse

FORMATION � Magmatic-ore formation

� Rare (most of the sulfides minerals crystallize from aqueous solutions at T < 600°C)

Fig. 24.7 in Wenk & Bulahk

� Crystal fractionation that forms levels (ex. Bushweld complex in South Africa)

FORMATION � Magmatic-ore formation

� Rare (most of the sulfides minerals crystallize from aqueous solutions at T < 600°C)

Source: http://www.science20.com/tuff_guy/magma_chambers_part_ii_magma_mushes-84812

� Crystal fractionation that forms levels (ex. Bushweld complex in South Africa)

FORMATION � Magmatic-ore formation

� Rare (most of the sulfides minerals crystallize from aqueous solutions at T < 600°C)

Fig. 24.7 in Wenk and Bulahk

� Crystal fractionation that forms levels (ex. Bushweld complex in South Africa)

� Formation of 2 immiscible liquids: silicate melt + sulfide melt

RECAP PART 1 & 2

� Part 1: Native elements

� Rare: 2ppm of Earth’s crust

� Close-packing

� Metal, semimetal, non metal

� Metal: gold group, platinum group and iron group

� Occurrences: Au & Ag – hydrothermal; Cu – mafic rock; Pt & Diamond: ultramafic; graphite – sedimentary metamorphic rock; Sulfur – fumaroles & salt domes

RECAP PART 1 & 2

� Part 2: Sulfides and related elements

� Large group: 600 minerals

� Most common source: hydrothermal deposits

� most common ore source � MpXr: - M is a metal or semimetal

- X can be: S, As, S+As, Te

PART 3: OXIDES, HYDROXIDES AND HALIDES Chapters 21 & 25 in Wenk & Bulakh

Chapter 18 in Nesse

OXIDES

� ~200 minerals � One or more metals +

oxygen � Mostly ionic crystal

structure (except ice) � High symmetry � Minor constituents of rocks

OXIDES � X2O group � Ice H2O

� Unit cell: hexagonal � Structure: unusual: H2O molecules

bonds together with H bonds ⇒ each water molecule coordinate with 4 other ones (tetrahedron)

� Form: granular or snow flakes (fractal)

� Use: Nesse (2000), p. 392: “Perhaps its most important use is to cool the drinks that slake the thirst of geologists after long hot days in the field.”

OXIDES � X2O group � Cuprite Cu2O

� Unit cell: hexagonal � Structure: Anion: body-centered

Cations: in the center of each “sub- cubes” – only half of the sites occupied

� Color: Ruby-red to almost black � Streak: brownish red � Thin section: red to yellow, relief +++ � Occurrence: near-surface oxidized portion of copper-

bearing hydrothermal sulfide deposits

OXIDES � Spinel group: XY2O4

� X (divalent cation): 8 tetrahedral sites � Y (trivalent cation): 16 octahedral sites � O2- : ccp (=fcc) � Magnetite series: inverse spinel structure

� γ-Mg2SiO4: high pressure polymorph of olivine with spinel structure

Spinel series Chromite series Magnetite series

XAl2O4 XCr2O4 XFe2O4

Spinel: MgAl2O4 Chromite: FeCr2O4 Magnetite: FeFe2O4

X = Mg, Fe, Zn, Mn X = Fe or Mg X = Fe, Mg, Zn, Mn, Ni

+ FeFeTiO4, MnMn2O4

OXIDES

� Spinel group: XY2O4 � Spinel: (Fe,Mg)Al2O4

� Unit cell: isometric � Solid-solution – Cr3+ can substitute to Al3+

� Form: octahedron � Luster: vitreous � Color: Green – blue-green � Thin section: Same color, relief +++

OXIDES

� Spinel group: XY2O4

� Spinel: (Fe,Mg)Al2O4

� Unit cell: isometric � Solid-solution – Cr3+ can substitute to Al3+

� Form: octahedron � Luster: vitreous � Color: Green – blue-green � Thin section: Same color, relief +++

My cat!

OXIDES

� Spinel group: XY2O4 � Magnetite: FeFe2O4

� Unit cell: isometric � Solid-solution with Ti4+ :

Coupled substitution: Fe3+ ↔ Ti4+ and Fe3+ ↔ Fe2+

� Form: octahedron � Luster: Dull metallic to metallic � Color: Black � Thin section: opaque � Occurrence: very common in magmatic and metamorphic

rocks

OXIDES

� Spinel group: XY2O4 � Chromite: FeCr2O4

� Unit cell: isometric � Form: octahedron � Luster: metallic � Color/Streak: Black/Brown � Thin section: opaque to dark brown � Occurrence: mafic and ultramafic rocks � Use: only source of chromium (protection from corrosion)

Chromite-bearing dunite

OXIDES

� X2O3 group � Hematite (Fe2O3), Ilmenite (FeTiO3),

Corundum (Al2O3) � Structure: hcp of anions, cations in

octahedral sites � Layers of octahedra � Only 2/3 of octahedra sites are

occupied by cations � Occupied octahedra share 2 anions

(shared edges) � Occupied octahedra share 3 anions

with subsequent layer (shared face)

Fig. 18.6 in Nesse

OXIDES � X2O3 group � Hematite (Fe2O3) � Luster: metallic to earthy � Color: gray; Steak: red-brown � Thin section: opaque � Occurrence: produced by weathering or hydrothermal

alteration; can be found as minor constituent in some evolved mafic rocks

OXIDES � X2O3 group � Corundum (Al2O3) � Luster: vitreous to adamantine � Color: white, gray, gray-blue

red (ruby), blue (sapphire), yellow, green � Thin section: colorless, relief +++ � Occurrence: in igneous rocks (rare), Al-rich pelitic rock,

metamorphosed limestone

OXIDES � X2O3 group � Ilmenite (FeTiO3) � Luster: metallic � Color: black � Thin section: opaque � Occurrence: common accessory mineral in igneous and

metamorphic rock � Use: major Ti extraction: to produce brilliant white

pigment (TiO2)

OXIDES

� XO2 group � Rutile (TiO2), Cassiterite (SnO2) � Structure: tetragonal

� Chain of octahedra at each corner + one chain in the middle along the c-direction

� Octahedra in each chains share edges

� Octahedra between 2 chains share corner

Fig. 18.8 in Nesse

OXIDES

� XO2 group � Rutile (TiO2), Cassiterite (SnO2) � Structure: tetragonal

� Chain of octahedra at each corner + one chain in the middle along the c-direction

� Octahedra in each chains share edges

� Octahedra between 2 chains share corner

Fig. 18.8 in Nesse

OXIDES

� XO2 group � Rutile (TiO2) � Luster: metallic to adamantine � Color/streak: Red-brown/white � Thin section: relief +++ � Occurrence: common accessory mineral in igneous and

metamorphic rock

HYDROXIDES

� Very common minerals � Produced by weathering and hydration � 2 important minerals: Mg(OH)2 (brucite) and Al(OH)3

(gibbsite): starting point to describe the layer silicates (sheet silicates = phyllosilicates)

� OH-: arrange in planes � Cation (Mg or Al): octahedral

sites between the anion planes. � 2 planes of anions + the

interstitial anions form a neutral sheet

anion

Cation

HYDROXIDES

� Brucite (Mg(OH)2) � All the octahedral sites are

filled by cations � Structure: hexagonal � Cleavage: perfect on (001) � Luster: viterous or greasy � Color: white/blue/green - pale � Relief in thin section: ++ � Occurrence: mostly in marble,

also in serpentinite (alteration product of peridodite)

OH-

Mg2+

HYDROXIDES

� Gibbsite (Al(OH)3) � 2/3 of octahedral sites are

occupied � Structure: hexagonal � One of the main phase of

Bauxite: Important ore of Aluminum

HALIDES

� ~ 120 minerals � Anion: Cl, Br, F or I (large radius) � Mostly ionic compound – simple structures � 3 common halides:

� Halite (NaCl) � Fluorite (CaF2) � Sylvite (KCl)

� Occurrence: evoporites

� Halite (NaCl) � Structure:

� 2 interconnected fcc � Na: Octahedral coordination

� Composition: mostly pure – minor substitution of Na+ fo K+

� Properties: � Form: cube � Vitreous, colorless if pure, relief: +

� Occurrence: evaporite � Use: food, road, manufacture of

industrial chemicals

� Sylvite (KCl) � Structure:

� 2 interconnected fcc � K+: Octahedral coordination

� Composition: mostly pure – minor substitution of K for Na or of Cl for Br

� Properties: � Form: cube � Vitreous, colorless/white if pure, relief: --

� Occurrence: evaporite (much less abundant than halite)

� Use: fertilizer to provide potassium

ORIGIN: EVAPORITE � Evaporite: chemical precipitates from the

evaporation of supersaturated solutions � Source of most halide (except fluoride) � Halite: the most common halide– beds:

100’s → 1000m thick � Evaporite: limestone + gypsum beds +

rock salt + various amount of terrigenous sediments

� Chemistry of the lakes depends on the chemistry of the water that fed the saline lakes.

� Ex.:- Green River (Wyoming): thick bed of trona (Na+ and HCO3

-)

- Death Valley: borax (water enriched in boron) - Mediterranean basin (halite due to see water)

� Fluorite (CaF2) � Structure:

� F- anions form layers stack on the top of each other to form a cube

� Ca2+: in the space created between for anion: coordination8 (cubic) – occupied half of the sites.

� Fluorite (CaF2) � Structure:

� F- anions form layers stack on the top of each other to form a cube

� Ca2+: in the space created between for anion: coordination8 (cubic) – occupied half of the sites.

� Ca2+: organized as a fcc

� Fluorite (CaF2) � Structure:

� F- anions form layers stack on the top of each other to form a cube

� Ca2+: in the space created between for anion: coordination8 (cubic) – occupied half of the sites.⇒Ca2+: organized as a fcc

� Composition: mostly pure � Color: colorless, blue, purple, green, or

others – Fluorescent � Occurrence : associated with sulfides –

hydrothermal deposit

� Fluorite (CaF2) � Structure:

� F- anions form layers stack on the top of each other to form a cube

� Ca2+: in the space created between for anion: coordination8 (cubic) – occupied half of the sites.⇒Ca2+: organized as a fcc

� Composition: mostly pure � Color: colorless, blue, purple, green,

or others – Fluorescent � Occurrence : associated with sulfides –

hydrothermal deposit

RECAP PART 3: OXIDES, HYDROXIDES AND HALIDES

� Oxides: Metals + oxygen � X2O group (X = H or Cu) � Spinel group: XY2O4:

�  spinel series XAl2O4

�  chromite series XCr2O4

� Magnetite series XFeO4

� X2O3 group: Hematite (Fe2O3), Ilmenite (FeTiO3), Corundum (Al2O3)

� XO2 group: rutile (TiO2)

RECAP PART 3: OXIDES, HYDROXIDES AND HALIDES

� Hydroxides: Brucite (Mg(OH)2) and gibbsite (Al(OH)3) � OH-: arrange in planes � Cation (Mg or Al): octahedral sites between the anion planes

� Halides: Halite (NaCl), Fluorite (CaF2), Sylvite (KCl) � NaCl and KCl: isostructural – 2 fcc interconnected – found in

evaporites � CaF2: layer of anions with cations in cubic sites between the

layers – found in hydrothermal deposits

PART 4: CARBONATES, SULFATES & PHOSPHATES Chapters 22 & 23 in Wenk & Bulakh

Chapter 17 in Nesse

INTRODUCTION

� All based on anionic groups – net charge from -2 to -5 � Carbonates: CO3

2- ↔ 3 oxygen around C4+ in a triangular arrangement

� Sulfates: SO42-

� Phosphates: PO43-

� Tungstates: WO42-

� Molybdates: MoO42-

� Borates: BO33- or BO4

5- → B3+ coordinate with O2- or OH-

Oxygens form a tetrahedron around the cation

CARBONATES � One common radical: XO3

n-

� ~ 170 minerals � Simple carbonates – no other anion Ex.: calcite (CaCO3), dolomite (CaMg(CO3)2) � Complex carbonates: additional anions Ex.: malachite (Cu(CO3)(OH)2) � Other minerals with the radical XO3

2-: nitrates, some borates

� 4 groups of carbonates: calcite, dolomite, aragonite and hydrated carbonates

CARBONATES

� Calcite and dolomite groups: � Same structure: rhombohedral carbonates.

Fig. 17.2 Nesse (2000)

Calcite: M2+ = Ca2+ Dolomite

From halite: 1)  Cube shortened along c

axis to form rhombohedron (A3)

2)  Na+ replaced by M2+

3)  Cl- replaced by CO32-

4)  CO32- arrangements

perpendicular to c-axis 5)  C4+ form ccp

CARBONATES � Calcite group:

� Calcite (CaCO3): �  Important rock forming mineral �  Occurrence: sedimentary rock (limestone, chalk, sandstones), cave

deposits, hydrothermal veins, metamorphic rock (marble), carbonatite �  Use: cement, lime, mortar

� Magnesite (MgCO3) �  Alteration product of Mg-rich igneous and metamorphic rocks �  Use: rock-climbing

� Siderite (FeCO3) �  In sedimentary rock – Source of Fe

� Rhodocrosite (MnCO3), Smithonite (ZnCO3)

CARBONATES

� Dolomite group: � Dolomite (CaMg(CO3)2):

� Occurrence: sedimentary rock - secondary (dolomitization: transformation of calcite into dolomite), in hydrothermal veins, carbonatite

� Ankerite (CaFe(CO3) � Common in pre-Cambrian Fe metamorphic formation � Occurrence: hydrothermal veins, in fractures of clays or

shales, carbonatites

CARBONATES

� Aragonite group: � structure: orthorhombic

1)  CO32- form layers

perpendicular to c-axis 2)  Cations: in 9-fold sites

(CN = 9): non common – to accommodate large cations

CARBONATES � Aragonite group:

� Aragonite (CaCO3): � HP-HT polymorph of calcite �  Form: usually columns of needles � Occurrence: Blue-schist � Witherite (BaCO3) and Strontianite (SrCO3) � Rare �  In hydrothermal deposit

� Witherite (BaCO3) and Strontianite (SrCO3) � Rare �  In hydrothermal deposit

CARBONATES

� OH-bearing group: � Monoclinic � Azurite (Cu2CO3(OH)2) and malachite (Cu3(CO3)2(OH)): mineral

collection � Only in oxidized portion of cooper-bearing hydrothermal sulfide

deposits � Other occurrence: evaporite

SULFATES

� S serve as a native element in sulfur, as a anion in sulfide and as a cation in sufates (S6+)

� Only 3 common sulfates: Gypsum, anhydrite and barite

SULFATES � Gypsum CaSO4∙2H2O

� Structure: monoclinic � Twinning: swallowtail � Dehydration: anhydrite � Occurrence: marine evaporite � Use: to produce wallboard: cover of the wall in houses of

North america – fortified the walls � Gypsum: can be responsible for the formation of sinkholes

and caves � Anhydrite CaSO4

� Structure: orthorhombic � Hydration: gypsum � Occurrence: marine evaporite

SULFATES

� Barite BaSO4 � Structure: orthorhombic � Intergrowth of crystals can form rosettes � Relatively high density � In veins of hydrothermal deposits � Rare � Primary source of Barium � used in “drilling mud that take advantage of the high

density

PHOSPHATES

� PO43- with the cation P5+

� Common phosphates: Apatite, monzanite and xenotime + Turquoise in mineral collection (rare)

PHOSPHATES

� Apatite Ca5(PO4)3(OH,F,Cl) � Structure: hexagonal � Widespread accessory mineral � Occurrence: nepheline-bearing rocks (largest amounts)

granite, pegmatite and marble (biggest crystals) � Composition: change in amount of OH, F and Cl � Use: fertilizer � Important bio-mineral: constituent of bones and teeth with

carbonate. � Important mineral in Petrology: volatile and water content in

apatite used to prove the presence of water on Moon

PHOSPHATES � Monzanite (Ce, La, Th)PO4

� Structure: monoclinic � Occurrence: accessory mineral in granite, pegmatite, syenite (Ne-

lava) and carbonatite. Because resistant to weathering: in the clastic part of sediments. In metamorphic rock (dolostone, mica shits, gneiss and granulites)

� Use: primary source of Th, Ce and other REE

� Xenotime YPO4 � Structure: tetragonal � Can be misidentify with zircon (lower n) � Occurrence: accessory mineral in granite, syenite and related

rocks, and in micas and gneiss � Use: source of ytrium –to produce phosphors in fluorescent light

(old-style color television and computer screen)