UNIVERSITY OF SOUTH ALABAMA
GY 302: Crystallography &
Mineralogy
Lecture 15: Carbonates, Nitrates,
Borates
Instructor: Dr. Douglas Haywick
Last Time (before the break)
Halides
Select minerals
Occurrences and Associations
Featured minerals: Evaporites
Halide Minerals
Halite (NaCl)
Crystal: Isometric
─
Pt. Group: 4/m 3 2/m
Habit: cubic, hopper crystals
SG: 2.17; H: 2.5
L: vitreous; Str: white
Col: white (various shades)
Clev: perfect [100], [010], [001]
Optics: Isotropic (n=1.544)
Name derivation: From the Greek halos (salt)
Halide Minerals
Fluorite (CaF2)
Crystal: Isometric
─
Pt. Group: 4/m 3 2/m
Habit: cubic, octahedral crystals
SG: 3.0-3.25; H: 4
L: vitreous; Str: white
Col: variable
Clev: [111] perfect
Optics: Isotropic (n=1.434)
http://www.electric-lady-land.com/004.%20Fluorite-LW.jpg
Name derivation: From its elemental composition containing fluorine
Evaporite Formation
First
Aragonite (ooids)
Dolomite
Gypsum
Anhydrite
Halite
Last
Sylvite*
Today’s Agenda
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
Carbonates, Nitrates, Borates
•There are 70 carbonate minerals, over 60 borates and a few
nitrates
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
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, Nitrates, Borates
•Carbonates are by far the most important of the Class V
minerals, three of which (calcite, dolomite and aragonite)
comprise about 40% of all sedimentary rocks and more than
20% of the entire geological column.
•They are both biogenic and chemically precipitated
Carbonates
Calcite Group (3 2/m):
Calcite (CaCO3)
Magnesite (MgCO3)
Siderite (FeCO3)
Rhodochrosite (MnCO3)
Smithsonite (ZnCO3)
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)
Dolomite Group (3):
Calcite and Dolomite both
possess 6-fold
(Octahedral) coordination
Dolomite (CaMg(CO3)2)
The only difference is that
Ankerite (CaFe(CO3)2)
dolomite lacks 2/m
Kutnahurite (CaMn(CO3)2)
Zincian Dolomite (CaZn(CO3)2) symmetry because of
alternating Ca-Mg layers
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
Calcite (CaCO3)
Crystal: Trigonal
─
Pt. Group: 3 2/m
Habit: euhedral (rhombs); scalenohedral
(“dog tooth”), bladed, stalactitic, massive
SG: 2.71; H: 3
L: vitreous, waxy; Str: white
Col: white (various shades)
Clev: {101} Perfect
Optics: uniaxial ne= 1.486; nw= 1.658
Name derivation: From the Latin, calx, meaning lime
Carbonate Minerals
Calcite (CaCO3)
Occurrence: widespread sedimentary and
epithermal breccia (MVT) deposits; biogenic
mineral (trilobites, echinoderms etc.)
Associated Mins: sedimentary: dolomite,
aragonite, quartz; MVT: dolomite, sphalerite,
galena, fluorite
May be confused with: most rhombohedral
carbonates (possibly distinguished because of
its reactivity with HCl)
Uses: many
Carbonate Minerals
Calcite is used for:
1) Polarizing filters in optics (Iceland spar)
2) a flux in steel manufacturing
3) building materials, floor tiles, marble vanities
4) Portland cement
Carbonate Minerals
Calcite is used for:
1) Polarizing filters in optics (Iceland spar)
2) a flux in steel manufacturing
3) building materials, floor tiles, marble vanities
4) Portland cement
CaCO3
<10% Mg
0% Pyrite
heat
CaO
Carbonate Minerals
Calcite is used for:
1) Polarizing filters in optics (Iceland spar)
2) a flux in steel manufacturing
3) building materials, floor tiles, marble vanities
4) Portland cement
CaCO3
CaO + clay
burned
“clinker”
Carbonate Minerals
Calcite is used for:
1) Polarizing filters in optics (Iceland spar)
2) a flux in steel manufacturing
3) building materials, floor tiles, marble vanities
4) Portland cement
CaCO3
CaO + clay
“concrete”
“clinker”
Carbonate Minerals
Dolomite (CaMg(CO3)2)
Crystal: Trigonal
─
Pt. Group: 3
Habit: euhedral rhombohedral, saddles
SG: 2.86; H: 3.5
L: vitreous; Str: white
Col: white to grey, pink
Clev: {101} Perfect
Optics: uniaxial ne= 1.500; nw= 1.680
Name derivation: French mineralogist Deodat Guy Tancrede Gratet de Dolomieu (1750-1801)
Carbonate Minerals
Dolomite (CaMg(CO3)2)
Occurrence: widespread sedimentary and
epithermal breccia (MVT) deposits,
replacement mineral, synsedimentary sabkha
deposits (pseudo-dolomite)
Associated Mins: sedimentary: calcite,
gypsum, anhydrite, aragonite; MVT: calcite,
sphalerite, galena, fluorite
May be confused with: most rhombohedral
carbonates
Uses: agriculture
Carbonate Minerals
The Dolomite Problem
(A) Schematic side view of the dolomite (104) surface. (B) Lateral-force microscopy image of a
dolomite surface with pristine and reacted regions, imaged during reaction. The reaction
effectively stops when the surface is coated by the reaction product. (C) Real-time X-ray reflectivity
data of dolomite in saturated and supersaturated solutions, showing the reaction kinetics, the selflimiting reaction and the irreversibility with respect to the pristine surface, R(t)/R(0) = 1.
http://www.cse.anl.gov/nuclear_enviro_processes/interfacial_processes/dolomite_problem.html
Discussion
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
Carbonate Minerals
Aragonite (CaCO3)
Occurrence: blueschist metamorphic
facies; common biogenic mineral
(corals, bivalves, etc.)
Associated Mins: metamorphic
assemblage: glaucophane, pumpellyite
May be confused with: calcite
Uses: none
Calcite-Aragonite stability field
http://www.geol.lsu.edu/henry/Geology3041/lectures/26MetaReactions/Fig26-1.jpg
Carbonate Minerals
Rhodochrosite (MnCO3)
Crystal: Hexagonal (Trigonal)
─
Pt. Group: 3 2/m
Habit: botryoidal, banded, euhedral
(rhombs); massive
SG: 3.69; H: 4
L: vitreous, waxy; Str: white
Col: pink, pinkish red, yellow
Clev: {101} Perfect
Optics: uniaxial ne= 1.596; nw= 1.816
Name derivation: From the Greek rhodon for rose and chroma for color.
Carbonate Minerals
Rhodochrosite (MnCO3)
Occurrence: epi- to mesothermal ore deposits
in igneous host rocks; high temperature
metamorphic rocks
Associated Mins: copper sulfides, galena,
sphalerite, barite
May be confused with: rhodonite (H=6)
Uses: secondary ore of Mn
Carbonate Minerals
Smithsonite (ZnCO3)
Crystal: Hexagonal (Trigonal)
─
Pt. Group: 3 2/m
Habit: botryoidal
SG: 4.5; H: 4.5
L: vitreous, waxy; Str: white
Col: blue, grey, grayish white
Clev: {101} Perfect
Optics: uniaxial ne= 1.625; nw= 1.850
Name derivation: After James Smithson (1765-1829), English mineralogist who financed the Smithsonian!
Carbonate Minerals
Smithsonite (ZnCO3)
Occurrence: secondary ore mineral in oxidized
zinc deposits (supergene?)
Associated Mins: hemimorphite, cerrusite,
anglesite, pyromorphite
May be confused with: hemimorphite
Uses: secondary ore of Zn
Carbonates, Nitrates, Borates
Borate Minerals
Borax (Na2B4O7·10H2O)
Crystal: Monoclinic
Pt. Group: 2/m
Habit: massive, prismatic (rare)
SG: 1.71; H: 2 to 2.5
L: earthy, vitreous; Str: white
Col: blue, grey, grayish white
Clev: [100], [110] Perfect
Optics: Biaxial nα= 1.447; nβ= 1.469; nγ= 1.472
Name derivation: From the Arabic buraq, for white.
Borate Minerals
Borax (Na2B4O7·10H2O)
Occurrence: evaporite mineral (playas)
Associated Mins: Kernite, Colemanite (other
borates)
May be confused with: lots, but it is soluble
Uses: source of boron, chemicals
Nitrate Minerals
Nitratine (NaNO3)
Crystal: Trigonal
─
Pt. Group: 3 2/m
Habit: massive, granular
SG: 2.26; H: 1.5-2
L: vitreous; Str: white
Col: white, brown, yellow
Clev: {101} Perfect
Optics: uniaxial ne= 1.580; nw= 1.330
Name derivation: duh…
Nitrate Minerals
Nitratine (NaNO3)
Occurrence: extremely arid playa lakes
in Chile
Associated Mins: gypsum, halite, niter,
iodate minerals
May be confused with: N/A
Uses: fertilizer
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….
MVT-ores
Some of the most
spectacular mineral
specimens come from
MVT mines.
Euhedral crystals
indicate significant pore
space was present during
mineralization
MVT-ores
Galena (PbS)
Sphalerite (ZnS)
MVT-ores
MVT-ores are
common
around the
world
MVT-ores
Saddle dolomite
Sphalerite
Original country rock
(dolostone)
Country rock is almost
always brecciated
MVT-ores
Chalk Board
Today’s Stuff To Do
1.
Poster preparation discussion (1 hr)
2.
Carbonates and Halides in lab
Online
1.
Sulfates and Phosphates (Lecture 15)
Thursday
1.
Test or writing assignment
GY 302: Crystallography and
Mineralogy
Lecture 15: Carbonates etc.
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposes.
For personal use only.