Lecture 3 - Mineralogy .
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Transcript of Lecture 3 - Mineralogy .
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Lecture 3 - Mineralogy
http://www.soest.hawaii.edu/coasts/gg101/index.html
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Atoms build
Molecules build
Minerals build
Rocks buildEarth’sCrust
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Common minerals that we mine and use.
Mineral Name What It Is Uses
Challcopyrite Copper-iron-sulfur mineral; CuFeS2 Mined for copper
Feldspar Large mineral family; aluminum-silicon-oxygen composition; decomposes to form clays; x(Al,Si)3O8, where x = various elements
like sodium, iron
Ceramics and porcelain
Fluorite Calcium-fluorine mineral; CaF2 Mined for fluorine (its most important ore); steel manufacturing
Galena Lead and sulfur mineral; PbS, the leading ore for lead
Mined for lead
Graphite Pure carbon; C, Pencil “lead” (replacing the actual lead metal once used in pencils); dry lubricant
Gypsum Hydrous-calcium-sulfur mineral; CaSO4 –
2H2O
Drywall, plaster of Paris
Halite Sodium-Chloride; NaCl Table salt, road salt, sodium, chlorine
Hematite Iron-oxygen mineral; Fe2O3 Mined for iron
Magnetite Iron-magnesium-oxygen mineral; (Fe,Mg)Fe2O4
Mined for iron
Pyrite Iron-sulfur mineral; FeS2 Mined for sulfur and iron
Quartz Silicon-oxygen mineral; SiO2 In pure form, for making glass
Sphalerite Zinc-iron-sulfur mineral; (Zn,Fe)S Mined for zinc
Talc Magnesium-silicon-oxygen-hydrogen mineral; Mg3Si4O10(OH)2
Used in ceramics, paint, talcum powder, plastics and lubricants
Calcite Calcium carbonate CaCo3 Toothpaste, cement, drywall
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Bingham Copper Mine – copper, silver, gold, molybdenum
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What is a Mineral?A mineral is a naturally occurring, inorganic solid with an orderly internal arrangement of atoms (called crystalline structure) and a definite, but sometimes variable, chemical composition
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Hawaii’s most common mineral – volcanic Olivine
Hawaii’s second most common mineral – marine Calcite
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Eight Abundant Elements in Crust
oxygen 46% (O2-)
silicon 28% (Si4+)
aluminum 8% (Al3+)
iron 6% (Fe2+ or Fe3+)
magnesium 4% (Mg2+)
calcium 2.4% (Ca2+)
potassium 2.3% (K1+)
sodium 2.1% (Na1+)
How are minerals built?
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Review the structure of an atom
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Structure of the Atom -
8
If we drew a hydrogen atom to scale, making the nucleus the diameter of a pencil, the electron would orbit about 0.5 km from the nucleus. The whole atom would be the size of a baseball stadium…with so much empty space, how canour world feel so solid?
Octet Rule…filled outer orbitalAtomic Number…number of protonsMass Number…number of protons and neutrons
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Isotopes of an atom have variable number of neutrons (mass number)
Most atoms exist in a charged state due to the need to have a filled outer shell - Ions
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Eight Abundant Elements in Crust
oxygen 46% (O2-)
silicon 28% (Si4+)
aluminum 8% (Al3+)
iron 6% (Fe2+ or Fe3+)
magnesium 4% (Mg2+)
calcium 2.4% (Ca2+)
potassium 2.3% (K1+)
sodium 2.1% (Na1+)
How are minerals built?
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Octet Rule
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Chlorine = 7 electrons in outer shellSodium = 1 electron in outer shell
NaCl
Ionic Bonding
7 e- in outer shell
1 e- in outer shell
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Covalent Bonding
Oxygen = 6 electrons in outer shellHydrogen = 1 electron in outer shell
H20
Polar molecule
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46% oxygen (O2-)28% silicon (Si4+)8% aluminum (Al3+)6% iron (Fe2+ or Fe3+) 4% magnesium (Mg2+)2.4% calcium (Ca2+)2.3% potassium (K1+)2.1% sodium (Na1+)
These elements in a magmachamber bond and form minerals as the magma loses heat
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Slow cooling allows fewer (larger)crystals = coarse texture to rock
Rapid cooling leads to many small crystals = smooth texture to rock
Crystallization
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Most abundant elements? – silicon and oxygen
Silicon has 4 electrons in outer shell = needs 4 more.
Oxygen has 6 electrons in outer shell = needs 2 more.
Oxygen still needs 1 more electron each
(SiO4)4-
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Silica tetrahedrons will form minerals with crystalline structure consisting of unlinked tetrahedra, chains, double chains, and sheets.
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Chains of silicatesform because Oxygen bonds with Silicon a second time
Single tetrahedron
Single chain
Double chain
Silicate sheet
(SiO4)4-
(SiO3)2-
(Si4O11)6-
(Si2O5)2-
Three-dimensionalframework (Si3O8)4-
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Silicon tetrahedrons form chains
Metallic cations fit inside the chains
(SiO3)2-
aluminum (Al3+)iron (Fe2+ or Fe3+) magnesium (Mg2+)calcium (Ca2+)potassium (K1+)sodium (Na1+)
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Pairs of cations thatsubstitute for eachother
Cations move into spaces in silicate structures, butthey will only form compounds that have no charge – neutral(positive charges must equal negative charges)
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Silicon tetrahedrons form chains
Metallic cations fit inside the chains
(SiO3)2-
aluminum (Al3+)iron (Fe2+ or Fe3+) magnesium (Mg2+)calcium (Ca2+)potassium (K1+)sodium (Na1+)
One cation maypush another out of the latticework
SubstitutionMg
Fe
CaNa
Single substitution
Double substitution
Si
Al
Must result in aneutral compound
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Charge Size (nm)46% oxygen (O2-) 0.1322.3% potassium (K1+) 0.133
6% iron (Fe2+ or Fe3+) 0.0644% magnesium (Mg2+) 0.066
28% silicon (Si4+) 0.0428% aluminum (Al3+) 0.050
2.4% calcium (Ca2+) 0.0992.1% sodium (Na1+) 0.097
Cation Substitution: Mineral must be neutral
Na/Ca, Al/Si and Fe/Mg
Olivine: single tetrahedron (SiO4)4-
[Fe22+(SiO4)4-] or [Mg2
2+(SiO4)4-] +4 +4 –8=0 or +4 +4 –8=0
Atoms ina pair pusheach otherout ofposition
Feldspar: 3-D framework (Si3O8)4-
[Na1+Al3+Si34+O8
2-]or [Ca2+Al23+Si2
4+O82-]
+1 +3 +12 –16=0 or +2 +6 +8 –16=0
SingleSubstitutionFe Mg
Double Na CaSubstitution Al Si
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As the Si and O build crystalline structures and the metallic cations play single and double substitution, the entire magma chamber grows into a solid mass of minerals….