lecture 3 - mineralogy
TRANSCRIPT
Lecture 3 - Mineralogy
http://www.soest.hawaii.edu/coasts/gg101/index.html
Atoms build
Molecules build
Minerals build
Rocks buildEarth’sCrust
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
Bingham Copper Mine – copper, silver, gold, molybdenum
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
Hawaii’s most common mineral – volcanic Olivine
Hawaii’s second most common mineral – marine Calcite
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?
Review the structure of an atom
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
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
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?
Octet Rule
Chlorine = 7 electrons in outer shellSodium = 1 electron in outer shell
NaCl
Ionic Bonding
7 e- in outer shell
1 e- in outer shell
Covalent Bonding
Oxygen = 6 electrons in outer shellHydrogen = 1 electron in outer shell
H20
Polar molecule
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
Slow cooling allows fewer (larger)crystals = coarse texture to rock
Rapid cooling leads to many small crystals = smooth texture to rock
Crystallization
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-
Silica tetrahedrons will form minerals with crystalline structure consisting of unlinked tetrahedra, chains, double chains, and sheets.
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-
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+)
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)
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
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
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….