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Classroom presentations to accompany Understanding Earth , 3rd edition. prepared by Peter Copeland and William Dupré University of Houston. Chapter 2 Minerals: Building Blocks of Rocks. Minerals: Building Blocks of Rocks. Breck P. Kent.
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Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 2 Minerals: Building Blocks of Rocks
Minerals: Building Blocks of Rocks Breck P. Kent
A naturally occurring, inorganic solid with an ordered internal structure and a narrow range of chemical composition Mineral
Rock A naturally occurring consolidated mixture of minerals or mineral-like substances
A rigid sphere about 1 angstrom (Å) in diameter -- an angstrom is 10-10 m At the center of an atom is a nucleus which contains most of the mass of the atom Protons with a positive charge Neutrons with no charge -- neutral Quarks and other interesting things Atoms
Electrons(E): negative charge, very little mass Protons(Z): positive charge, mass 1832 times greater than electron Neutrons(N): no electric charge, mass 1833 times greater than electron Atoms
Abundance of the elements (wt. %) Crust Whole Earth Oxygen 46.3 % 29.5% Silicon 28.2% 15.2% Aluminum 8.2% 1.1% Iron 5.6% 34.6% Calcium 4.1% 1.1% Sodium 2.4% 0.6% Potassium 2.1% 0.1% Magnesium 2.3% 12.7% Titanium 0.5% 0.1% Nickel trace 2.4% All others trace 2.7%
Electrons orbit around the nucleus in discrete shells. Atomic structure Nucleus: protons, neutrons
First level (K) 2 electrons Second level (L) 8 electrons Third level (M) 18 electrons Fourth level (N) 32 electrons Energy-level shell:the space occupied by electrons of a particular energy level
L K Fig. 2.2b
L K Fig. 2.2c
Chemical characteristics of elements determined largely by number of protons # of protons = atomic number (A) # of neutrons (N) + A = atomic weight (Z) Atomic structure
Ion An electrically charged particle composed of an atom that has either lost or gained electron(s) to or from another atom.
Ions When an atom loses or gains an electron it is called an ion. Positively charged ions (loss of electron) are called cations. Negatively charged ions (gain of electron) are called anions.
Important ions in minerals anions charge cations charge Si +4 K +1 Ca +2 Na +1 Al +3 Mg +2 Fe +2 or +3 O -2
Ionic Attraction Forms NaCl (Halite) Fig. 2.4c
Electron Sharing in Diamond Fig. 2.5
Oxygen O Magnesium Mg Silicon Si Iron Fe Aluminum Al Sodium Na Potassium K Calcium Ca Carbon C Titanium Ti Hydrogen H Argon Ar Uranium U Zirconium Zr Strontium Sr Lead Pb Chemical Symbols
Periodic Table of Elements Fig. 2.6
(H+) (Na+) P = Proton N = Neutron Fig. 2.7 (Mg2+)
(O2-) P = Proton N = Neutron (Cl-) Fig. 2.7
Carbon Tetrahedron of Diamond Fig. 2.8a
Network of Carbon Tetrahedra Fig. 2.8b
Ultrahigh Vacuum Scanning Tunneling Microscope Image of Galena Fig. 2.10 Kevin M. Rosso & Michael F. Hochella, Jr
Galena Fig. 2.10b Chip Clark
Perfect Crystals Halite (cube) Quartz (hexagonal) Fig. 2.11
Halite (Cubic) and Quartz (Hexagonal) Ed Degginger & Bruce Coleman Breck P. Kent
Quartz Geode Large space allows larger crystals Fig. 2.12 Chip Clark
Ionic Radii Determine Packing Geometry Fig. 2.13
Graphite Atomic Structure Crystal Form Ken Lucas, Visuals Unlimited Fig. 2.15a
Diamond Atomic Structure Crystal Form E.R. Degginger, Photo Researchers Fig. 2.15b
Polymorphs • Minerals with the same chemical composition but different structure. • e.g., diamond and graphite • andalusite, kyanite, and sillimanite
Polymorphs of Carbon P.L. Kresan
There are some 3,500 recognized minerals found on Earth. However, For our purpose, we can focus on about a dozen. Silicates - Si, O and other elements, the most abundant mineral group in the Earth’s crust Carbonates - Ca, Mg and CO3 Salts - NaCl Minerals: lots and lots of ’em
Four oxygens surrounding a silicon ion. These tetrahedra combine to make the framework of the silicates. Different combinations produce different structures. Silica-oxygen tetrahedra
Silicate Ion[SiO4] 4+ Fig. 2.16a
Olivine Chip Clark Isolated Tetrahedra Silcate (example: olivine) Fig. 2.17a
Sheet Silicate (example: mica) Fig. 2.17d
Framework Silicate(example: quartz) Fig. 2.18