Download GY 302 - University of South Alabama

UNIVERSITY OF SOUTH ALABAMA
GY 302: Crystallography &
Mineralogy
Lecture 15: Sulfates and Phosphates
(Class VI and VII Minerals)
Instructor: Dr. Douglas Haywick
Last time (before the test)
Carbonates, Nitrates, Borates
Select carbonate minerals
Sphalerite and galena (left over sulfides)
1.
2.
Featured mineral association: MVT-ores
(Mississippi Valley-type ores)
Carbonates, Nitrates, Borates
•There are 70 carbonate minerals, over 60 borates and a few
nitrates
•All 3 types of minerals involve planar anion groups….
•… with the exception of BO44- which is tetrahedral
•Oxygen atoms are strongly covalently bonded in the anion
(especially in CO32-), but bonding between the anion and the
cation is ionic
Carbonates
Calcite Group (3 2/m):
Calcite (CaCO3)
Magnesite (MgCO3)
Siderite (FeCO3)
Rhodochrosite (MnCO3)
Smithsonite (ZnCO3)
Dolomite Group (3):
Dolomite (CaMg(CO3)2)
Ankerite (CaFe(CO3)2)
Kutnahurite (CaMn(CO3)2)
Zincian Dolomite (CaZn(CO3)2)
Carbonates
Calcite Group (3 2/m):
Calcite (CaCO3)
Magnesite (MgCO3)
Siderite (FeCO3)
Rhodochrosite (MnCO3)
Smithsonite (ZnCO3)
Aragonite Group (2/m 2/m 2/m):
Aragonite (CaCO3)
Witherite (BaCO3)
Strontianite (SrCO3)
Cerussite (PbCO3)
Carbonate Minerals
Aragonite (CaCO3)
Crystal: Orthorhombic (pseudo hexagonal)
Pt. Group: 2/m 2/m 2/m
Habit: euhedral, hexagonal prisms
SG: 2.94; H: 3.5-4
L: vitreous; Str: white
Col: colourless (pinkish)
Clev: poor{010}, {110}
Optics: Biaxial nα= 1.530; nβ= 1.682; nγ= 1.686
Name derivation: From its type location, Aragon in Spain
MVT-ores
Mississippi Valley-type ore
deposits
•Named after the type mines in
Missouri, Tennessee and other
sites in the Mississippi Valley
•Low temperature (epithermal)
sedimentary ore deposits
•Primary minerals produced:
dolomite (saddle), calcite,
fluorite and some old friends….
Today’s Agenda
Sulfates and Phosphates
1.
Class VI Minerals: Sulfates, Chromates, Molybdates, Tungstates
2.
Class VII Minerals: Phosphates, Arsenates and Vanadates
3.
Economics of Class VII minerals
Sulfates etc.
Sulfate Minerals
Gypsum (CaSO4·2H2O)
Crystal: Monoclinic
Pt. Group: 2/m
Habit: massive, fibrous, vitreous,
sand crystals
SG: 2.3; H: 2
L: vitreous to dull; Str: white
Col: colorless to grey
Clev: perfect {010}, weak {100}, {111}
Optics: Biaxial +
nα= 1.520; nβ= 1.522; nγ= 1.529
Name derivation: From the Greek, gyps meaning "burned" mineral. Selenite from the Greek in allusion to its pearly luster
(moon light) on cleavage fragments.
Sulfate Minerals
Gypsum (CaSO4·2H2O)
Occurrence: evaporite mineral; classic
sabkha deposit
Associated Mins: anhydrite, halite, dolomite
(evaporites)
Can be confused with: ulexite (satin spar)
Uses: building materials
Sulfate Minerals
Anhydrite (CaSO4)
Crystal: Orthorhombic
Pt. Group: 2/m 2/m 2/m
Habit: massive, fibrous (rare)
SG: 2.97;H: 3.5
L: vitreous to dull; Str: white
Col: colorless to grey
Clev: perfect [010]. [100], good [001]
Optics: Biaxial +
nα= 1.570; nβ= 1.576; nγ= 1.614
Name derivation: Greek anhydros, meaning "waterless"
Sulfate Minerals
Anhydrite (CaSO4)
Occurrence: evaporite mineral (related to
gypsum), less common in granite ore
bodies and altered igneous rocks
(“gangue”)
Associated Mins: gypsum, halite,
dolomite (evaporites); zeolites in altered
igneous rocks
Can be confused with: dolomite, calcite,
gypsum, barite
Uses: building materials
Sulfate Minerals
Celestine/Celestite (SrSO4)
Crystal: Orthorhombic
Pt. Group: 2/m 2/m 2/m
Habit: euhedral blocky crystals common
SG: 4.0; H: 3 to 3.5
L: vitreous; Str: white
Col: colorless to blue
Clev: perfect [001]; good [210]
Optics: Biaxial +
nα= 1.622; nβ= 1.624; nγ= 1.631
Name derivation: Latin coelestis, meaning “celestial"
Sulfate Minerals
Celestine/Celestite (SrSO4)
Occurrence: sedimentary deposits
(associated with evaporite minerals) and in
epithermal vein deposits. Rarer as a cave
precipitate.
Associated Mins: gypsum, halite, dolomite
(evaporites), sulfur, fluorite
Can be confused with: barite
Uses: principle source of strontium
Molybdate Minerals
Wulfenite (PbMoO4)
Crystal: Tetragonal
Pt. Group: 4/m
Habit: euhedral tabular crystals
SG: 6.75; H: 3
L: vitreous; Str: yellowish-white
Col: orange to yellow
Clev: poor [101]
Optics: uniaxial ne= 2.304; nw= 2.402
Name derivation: Named after the Austrian mineralogist, Frantz Xaver von Wulfen (1728-1805)
Molybdate Minerals
Wulfenite (PbMoO4)
Occurrence: secondary (supergene?)
product in lead and molybdenum sulfide
ore deposits
Associated Mins: pyromorphite,
vanadinite, calcite
Can be confused with: vanadinite
Uses: secondary source of Mo
Phosphates etc.
Phosphate Minerals
Apatite Group (Ca5(PO4)3(F,Cl,OH)
Fluorapatite (Ca5(PO4)3(F)
Crystal: Hexagonal
Pt. Group: 6/m
Habit: hexagonal crystals common, massive
SG: 3.19; H: 5
L: vitreous; Str: white
Col: you name it, you’ll see it
Clev: indistinct
Optics: uniaxial ne= 1.630; nw= 1.633
Name derivation: Greek apatao, meaning “misleading"
Phosphate Minerals
Apatite (Ca5(PO4)3(F,Cl,OH)
Occurrence: common. Igneous rocks,
metamorphic rocks, crusts in altered biogenic
remains (guano + coral)
Associated Mins: varied (reflects wide
occurrence)
Can be confused with: beryl, corundum;
diopside and olivine when massive
Uses: primary mineral source of phosphorus
(fertilizer)
Phosphate Minerals
Wavellite (Al3(PO4)2(OH)3·2H2O)
Crystal: Orthorhombic
Pt. Group: 2/m 2/m 2/m
Habit: acicular, radiating crystals, globular
SG: 2.34; H: 3.5-4
L: vitreous-waxy; Str: white
Col: shades of green/greenish yellow
Clev: prefect [110], good [101]
Optics: Biaxial +
nα= 1.530; nβ= 1.682; nγ= 1.686
Name derivation: Named after British mineralogist William Wavell (? To 1829)
Phosphate Minerals
Wavellite
(Al3(PO4)2(OH)3·2H2O)
Occurrence: secondary mineral in aluminumpoor metamorphic rocks (e.g., Arkansas)
Associated Mins: basic aluminum phosphates
Can be confused with: nothing I can think of
Uses: nothing
Phosphate Minerals
Pyromorphite (Pb5(PO4)3Cl)
Crystal: Hexagonal
Pt. Group: 6/m
Habit: globular to slender prismatic crystals
SG: 6.85; H: 3.5-4
L: vitreous to resinous; Str: white
Col: green, yellow to brown
Clev: imperfect
Optics: unaxial ne= 2.049; nw= 2.059
Name derivation: Greek for “fire” (pyr) and “form” (morfe)
Phosphate Minerals
Pyromorphite (Pb5(PO4)3Cl)
Occurrence: secondary minerals product in
oxidized zones of lead
Associated Mins: limonite, cerussite, malachite
Can be confused with: mimetite, malachite (if
you’re having a bad day)
Uses: bookendite
Vanadate Minerals
Vanadinite (Pb5(VO4)3Cl )
Crystal: Hexagonal
Pt. Group: 6/m
Habit: hexagonal to prismatic crystals
SG: 6.94; H: 3.5-4
L: vitreous; Str: brownish-yellow
Col: brown to orange to yellow
Clev: none
Optics: uniaxial ne= 2.35; nw= 2.416
Name derivation: Named for its vanadium content
Vanadate Minerals
Vanadinite (Pb5(VO4)3Cl )
Occurrence: secondary product in oxidized
galena ore deposits
Associated Mins: pyromorphite, wulfenite,
calcite
Can be confused with: wulfenite
Uses: secondary source of Vanadium
Phosphate Economics
“Phosphate Rock” (World Data) in 1000s of tons
Phosphate Chemistry
Phosphorite is a sedimentary (biogenic) rock
consisting of “collophane”, cryptocrystalline masses
of apatite group minerals:
Fluorapatite Ca5(PO4)3F
Hydroxyapatite Ca5(PO4)3OH
Chlorapatite Ca5(PO4)3Cl
Bromapatite Ca5(PO4)3Br
Florida is a major producer of PO43-
Phosphate Chemistry
Phosphorite is a
common marine
deposit....
e.g., Florida during the Miocene
“Phosphate Hardground”
http://oceanexplorer.noaa.gov/explorations/islands01/log/sep28/media/ledges.html
http://benkolstad.net/?p=2294
Phosphate Chemistry
But thick deposits are kind of rare and require sea level change:
•Upwelling brings nutrient laden
water onto the shelf
•slow sedimentation restricts
input of other materials (sea
level rise induced hiatus?)
•sea level fall removes CO32and organic material
nodular phosphate
http://www.oceanoasis.org/teachersguide/activity6.html
Phosphate Chemistry
Other types of phosphate/phosphorite formation:
•Bone beds
•Guano (“Island Deposits”)
•BIFs (Australia)
•Igneous (alkaline
intrusions +/- carbonate)
http://www.fao.org/docrep/007/y5053e/y5053e07.htm
GY 302: Crystallography and
Mineralogy
Lecture 15: Sulfates and Phosphates
Instructor: Dr. Doug Haywick
[email protected]
This is a free open access lecture, but not for commercial purposes.
For personal use only.