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 1. Select carbonate minerals 2. Sphalerite and galena (left over sulfides) 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…. 4- •… with the exception of BO4 which is tetrahedral •Oxygen atoms are strongly covalently bonded in the anion 2- (especially in CO3 ), 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 aluminum- poor 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 3- Florida is a major producer of PO4 Phosphate Chemistry Phosphorite is a e.g., Florida during the Miocene common marine deposit.... “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?) 2- •sea level fall removes CO3 and 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. .