UNIVERSITY OF SOUTH ALABAMA OF SOUTH ALABAMA . Lecture 9: Sulfides . Instructor: Dr. Douglas Haywick...

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GY 302: Crystallography & Mineralogy

UNIVERSITY OF SOUTH ALABAMA

Lecture 9: Sulfides

Instructor: Dr. Douglas Haywick

Last Time

Native elements 1. Chemistry and Crystallography (properties) 2. Occurrences and Associations 3. Economics (resources, reserves, extraction)

Featured Minerals: Gold

Native Elements

Copper Cu Isometric Gold Au* Isometric Silver Ag* Isometric Platinum Pt* Isometric Arsenic As Hexagonal Antimony Sb Hexagonal Bismuth Bi Hexagonal Tellurium Te Trigonal Sulfur S Orthorhombic Graphite C* Hexagonal Diamond C* Isometric

Metals

Semi-metals

Non-metals

* primary production from native elements

Metallic Native Elements

Gold (Au) Crystal: Isometric Pt. Group: 4/m32/m Habit: octahedral, dendritic SG: 15.6-19.3 (depending on Ag content)

H: 2.5-3* L: metallic Col: gold-yellow Str: gold-yellow Clev: none Optical: Opaque

Name Derivation: Anglo Saxon, of uncertain origin.

http://www.rocksandgems.info

Metallic Native Elements Resources: a concentration of a material useful to humanity (water, food, minerals) Geological Resources: all materials (mineral and energy) including those only surmised to exist, that have present or anticipated future value and which can be extracted from the Earth via economically feasible methods ($$$) (i.e., gold, diamonds, coal, oil, natural gas, water) Reserve Base: The in-place demonstrated (measured+indicated) amount of a resource that can be extracted via current mining and production techniques (currently economical + marginal +/- subeconomical). Equivalent to the old “geological reserve” definition. Reserve (current): That part of the reserve base that could be economically extracted today Production: refined metal produced per year (metric tons)

Metallic Native Elements Gold (production, reserves in tonnes*)

Production: refined metal produced per year (metric tons) *1 metric ton (tonne) = 1000 kg = 32,150.7 troy ounces

http://minerals.usgs.gov/minerals/pubs/mcs/2015/mcs2015.pdf

Metallic Native Elements Gold (US data)

2015 Mineral Commodity Summaries. USGS

Metallic Native Elements

Silver (Ag) Crystal: Isometric Pt. Group: 4/m32/m Habit: massive, acicular SG: 10.1-10.5 H: 2.5-3 L: metallic Col: silver-white Str: silver-white Clev: none Optical: Opaque

Name: Derivation: Anglo Saxon, of uncertain origin.

http://webmineral.com/specimens/picshow.php?id=1060

Metallic Native Elements Platinum Group (Pt, Ir, Pa, Rh, Ru, Os,) Crystal: Isometric Pt. Group: 4/m32/m Habit: massive, acicular SG: 21.47 H: 4-4.5 L: metallic Col: gray-silver Str: gray-silver Clev: none Optical: opaque

Name Derivation: Spanish, platina = "silver."

Non-metallic Native Elements

Graphite (C) Crystal: Hexagonal Pt. Group: 6/m 2/m 2/m Habit: platey, massive SG: 2.1-2.2 H: 1-2 L: submetallic Col: lead-gray, black Str: black Clev: perfect basal {001} Optical: opaque

Name derivation: From the Greek, graphein, "to write

Gold precipitation depends on: • Temperature • Pressure • pH • Cl- concentration of

hydrothermal solutions • H2S fugacity*

*pressure of an ideal gas which has the same chemical potential as the real gas. http://www.mawsonresources.com

Gold Gold is usually transported as [AuCl2

-] in systems hotter than 400 C. [Au(HS)2

-] is the dominant ion complex at lower temperatures

Maximum solubility occurs near the H2S-HS--SO4

2- equilibrium point

Gold Gold is usually transported as [AuCl2

-] in systems hotter than 400 C. [Au(HS)2

-] is the dominant ion complex at lower temperatures

(Zhu, An and Tan, 2011)

AU dissolution

Gold Precipitation of gold usually occurs following reduction in oxygen fugacity (Au-S complexes break down leading to precipitation of other sulfides like pyrite and precipitation of gold):

(Zhu, An and Tan, 2011)

AU precipitation

Gold Gold is largely produced through hydrothermal precipitation

http://gsc.nrcan.gc.ca/mindep/synth_dep/gold/vms/pdf/deposit_synthesis.gold_vms.dube.pdf

Gold Golden Giant Mine (Newmont)

Gold Extraction Cyanide Leeching Method

4Auo + 8CN- + O2 + 2H2O = 4Au(CN)2- + 4OH-

http://www.daa.com.au/uploads/RTEmagicC_mm_leachfeed.jpg.jpg

Gold Extraction Heap Cyanide

Leeching Method

Non-metallic Native Elements

Diamond (C) Crystal: Isometric Pt. Group: 4/m32/m Habit: octahedral, twinned SG: 3.5 H: 10 L: adamantine Col: colorless, rare blue,

red, yellow Str: n/a Optical: isotropic, n=2.419 Clev: perfect {111}

Diamonds

http://members.tm.net/lapointe/Carbon_Phase_Diagram.gif

Diamond Phase diagram

Diamond Kimberlite Pipes

http://www.kimcordiamonds.com/formation.php http://www.earth.ox.ac.uk/~oesis/field/medium/kimberlite.jpg

Diamonds

Diamond Kimberlite Pipes

http://www.kimcordiamonds.com/formation.php

http://gsc.nrcan.gc.ca/diamonds/kirkland/images/c14_3.jpg

Diamonds

http://gsc.nrcan.gc.ca/mindep/synth_prov/slave/pdf/regional_synthesis.slave.bleeker.pdf

Today’s Agenda

Sulfides and Sulfosalts 1. Properties of select sulfides/sulfosalts 2. Occurrences and Associations

Featured minerals: Cu-sulfides

Sulfides, Sulfosalts

and Arsenides

Sulfides, Sulfosalts and Arsenides Mineral Formula System Argentite Ag2S Isometric Arsenopyrite FeAsS Monoclinic Bornite Cu5FeS4 Tetragonal/ Isometric Boulangerite Pb5Sb4S11 Orthorhombic Chalcocite Cu2S Monoclinic Chalcopyrite CuFeS2 Tetragonal Cinnabar HgS Hexagonal Cobaltite CoAsS Isometric Covellite CuS Hexagonal Domeykite Cu3As Isometric Digenite Cu9S5 Hexagonal (trigonal) Enargite Cu3AsS4 Orthorhombic Galena PbS Isometric Jamsonite Pb4FeSb6S14 Monoclinic Marcasite FeS2 Orthorhombic Millerite NiS Hexagonal Molybdenite MoS2 Hexagonal Nickeline/Niccolite NiAs Hexagonal Orpiment As2S3 Monoclinic (combined with realgar) Pararamnelsbergite NiAs2 Orthorhombic Pyrite FeS2 Isometric Pyrrhotite Fe(1-x)S Variable Realgar AsS Monoclinic (combined with orpiment) Skutterudite/smaltite (Co,Ni)As2-3/(Co,Ni)As3x Isometric Sphalerite ZnS Isometric Stibnite Sb2S3 Orthorhombic Tetrahedrite (Cu, Fe)12Sb4S13 Isometric

Pb-ore

Zn-ore

Mo-ore

Ag-ore

Hg-ore

Co-ore

As-ore

Ni-ore

Ni-ore Ni-ore

Ni-ore

Cu-ore

Sulfides etc. Sulfides come in two distinct structural coordinations (and a third that is a more “complex” mixture of the two).

Sulfides etc. 1) Tetrahedral: S (and As) are closely packed and all metal ions are in tetrahedral coordination. Solid solutions are possible.

Sphalerite Chalcopyrite Bornite Enargite

Sulfides etc.

2) Octahedral: S (and As) are closely packed and all metal ions are in octahedral coordination.

Galena Pyrrhotite Niccolite

Sulfides etc. 3) Complex coordinations: either tetragonal or octahedral

Pentlandite Cobaltite Molybdenite Arsenopyrite Millerite Skutterudite Cinnabar Stibnite Covellite Tetrahedrite Argentite Orpiment Pyrite Realgar Marcasite

Sulfides etc. Cu-Fe sulfides

assemblages plot

Source: Perkins, D., 2002. Mineralogy. Second Ed., Prentice Hall, New Jersey, 483p.

Sulfides etc.

Tie lines connect minerals that normally co-exist under specific conditions of P and T

Cu-Fe sulfides assemblages plot

Sulfides etc.

Mineral assemblages found in ore deposits

Covellite/digenite/bornite assemblage

Cu-Fe sulfides assemblages plot

Covellite CuS Hexagonal Bornite Cu5FeS4 Isometric Chalcocite Cu2S Monoclinic

Today’s dog and pony mineral show features Copper Sulfides:

Sulfides etc.

Argentite Ag2S Isometric Pyrrhotite Fe(1-x)S Variable Realgar AsS Monoclinic Orpiment As2S3 Monoclinic Stibnite Sb2S3 Orthorhombic Arsenopyrite FeAsS Triclinic

Other sulfides worth mentioning (and showing):

Covellite (CuS) Crystal: Hexagonal Pt. Group: 6/m 2/m 2/m Habit: platy SG: 4.6 H: 1.5-2 L: metallic to submetallic Col: indigo blue Str: dark grey Clev: perfect (001)

Name derivation: After N. I. Covelli (1790-1829), who found the mineral on Mt. Vesuvius

Sulfide Minerals

Covellite (CuS) Occurrence: near surface hydrothermal deposits, porphyry igneous rocks (porphyry copper deposits). Associated Mins: bornite, chalcopyrite and pyrite Related Mins: forms solid solutions with klockmannite [CuSe] May be confused with: nothing

Sulfide Minerals

Bornite (Cu5FeS4) Crystal: Orthorhombic Pt. Group: 2/m2/m2/m Habit: tabular, commonly striated SG: 6 H: 3 L: metallic Col: bronze to iron black Str: dark grey to black Clev: poor {111}

Name derivation: After I. von Born (1742-1791), a German mineralogist

Sulfide Minerals

Bornite (Cu5FeS4) Occurrence: sulfide veins, secondary (enriched) sulfide deposits. Associated Mins: chalcopyrite, chalcocite, covellite, pyrrhotite, quartz and pyrite Related Mins: chalcopyrite [CuFe S2] May be confused with: niccolite, pyrrhotite, chalcocite and chalcopyrite

Sulfide Minerals

Chalcocite (Cu2S) Crystal: Monoclinic Pt. Group: 2/m Habit: massive SG: 5.8 H: 2.5-3 L: metallic Col: blue-white to lead grey Str: grey-black Clev: poor {110}

Name derivation: from the Greek chalkos meaning “copper”

Sulfide Minerals

Chalcocite (Cu2S) Occurrence: common primary and secondary mineral in sulfide veins and alteration zones. Associated Mins: bornite, enargite, galena, tetrahedrite, cuprite, chalcopyrite and pyrite Related Mins: digenite is a similar species [Cu2-xS] May be confused with: argentite and bornite

Sulfide Minerals

Copper

Copper Emplacement Copper ores are widely disseminated throughout the world. One of the more classic deposits was mined for decades near Butte Montana. •Porphyry copper deposit •Hydrothermal veins cross-cutting granites

Porphyry Copper Ores

Plate Tectonic Setting

John, D.A., (ed) 2010, Porphyry Copper Deposit Model, USGS Special Investigations Report 2010-5070-B; http://pubs.usgs.gov

1) Primary mineralization (hypothermal fluids ~400°C)

http://reynolds.asu.edu/sierra_cobre/p_formation.htm

2) Supergene mineralization (epithermal fluids ~25°C)

3) Burial

Sulfide Chemistry

Copper sulfide precipitation is controlled by 1) temperature (high to medium)

2) pH (acidity promotes Cu+ solution) 3) Sulfur content (as S2- or SO2)

4Cu+ + 4Fe2+ 8H2S +O2 →4CuFeS2 + 12 H+ +2H2O

Sulfide Chemistry

Other considerations:

1) Production of sericite [KAl2(Si3Al)O10(OH,F)2] is accelerated in acidic solutions and this lowers temperature of CuFeS2 formation

Sulfide Chemistry

2) Hornblende alters to biotite releasing more Fe2+ and promoting

precipitation of CuFeS2

Sulfide Chemistry

2) Hornblende alters to biotite releasing more Fe2+ and promoting

precipitation of CuFeS2

3) at high temperatures, SO2 content is higher than H2S content, but this changes as the temperature decreases to 400 °C:

4SO2 +4H2O →3H2SO4 + H2S

By the way.....

Gold can also be precipitated in porphyry copper assemblages: Gold transported as: AuSx

AuSxx+ + xH+ →Au0 + XH2S

x+ + 4Cu+ + 4Fe2+ + (x-1)H2S +O2 → Au0 + 4CuFeS2 + (12-x) H+ +2H2O

Covellite CuS Hexagonal Bornite Cu5FeS4 Isometric Chalcocite Cu2S Monoclinic

Today’s dog and pony mineral show features:

Porphyry Copper Deposits

Argentite Ag2S Isometric Pyrrhotite Fe(1-x)S Variable Realgar AsS Monoclinic Orpiment As2S3 Monoclinic Stibnite Sb2S3 Orthorhombic Arsenopyrite FeAsS Triclinic

Other sulfides worth mentioning (and showing):

John, D.A., (ed) 2010, Porphyry Copper Deposit Model, USGS Special Investigations Report 2010-5070-B; http://pubs.usgs.gov

Today’s Stuff To Do 1. Study your minerals

Today’s Lab

1. The Sulfides part 2 (lecture 10)

On Line Lecture

1. First look at minerals in lab! 2. Prep for our first mineral quiz next week

GY 302: Crystallography and Mineralogy

Lecture 9: Sulfides Part 1

Instructor: Dr. Doug Haywick dhaywick@southalabama.edu

This is a free open access lecture, but not for commercial purposes.

For personal use only.

UNIVERSITY OF SOUTH ALABAMA OF SOUTH ALABAMA . Lecture 9: Sulfides . Instructor: Dr. Douglas Haywick...

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