Earth s Crust. Atoms build Molecules build Minerals build. Rocks build. Lecture 3 - Mineralogy.

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1 Lecture 3 - Mineralogy Atoms build Molecules build Minerals build Rocks build Earth s Crust Common minerals that we mine and use. Mineral Name What It Is Uses Challcopyrite Copper-iron-sulfur mineral; CuFeS 2 Mined for copper Feldspar Large mineral family; aluminum-silicon-oxygen composition; decomposes to form clays; x(al,si) 3 O 8, where x = various elements like sodium, iron Ceramics and porcelain Fluorite Calcium-fluorine mineral; CaF 2 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; CaSO 4 2H 2 O Drywall, plaster of Paris Halite Sodium-Chloride; NaCl Table salt, road salt, sodium, chlorine Hematite Iron-oxygen mineral; Fe 2 O 3 Mined for iron Magnetite Iron-magnesium-oxygen mineral; (Fe,Mg)Fe 2 O 4 Mined for iron Pyrite Iron-sulfur mineral; FeS 2 Mined for sulfur and iron Quartz Silicon-oxygen mineral; SiO 2 In pure form, for making glass Sphalerite Zinc-iron-sulfur mineral; (Zn,Fe)S Mined for zinc Talc Magnesium-silicon-oxygen-hydrogen mineral; Mg 3 Si 4 O 10 (OH) 2 Used in ceramics, paint, talcum powder, plastics and lubricants Calcite Calcium carbonate CaCo 3 Toothpaste, cement, drywall Bingham Copper Mine copper, silver, gold, molybdenum 1

2 Hawaii s most common mineral volcanic Olivine 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 second most common mineral marine Calcite How are minerals built? Eight Abundant Elements in Crust Review the structure of an atom oxygen 46% (O 2- ) silicon 28% (Si 4+ ) aluminum 8% (Al 3+ ) iron 6% (Fe 2+ or Fe 3+ ) magnesium 4% (Mg 2+ ) calcium 2.4% (Ca 2+ ) potassium 2.3% (K 1+ ) sodium 2.1% (Na 1+ ) 2

3 Structure of the Atom Isotopes of an atom have variable number of neutrons (mass number) 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 can our world feel f so solid? i? Octet Rule filled outer orbital Atomic Number number of protons Mass Number number of protons and neutrons Most atoms exist in a charged g state due to the need to have a filled outer shell - Ions How are minerals built? Octet Rule 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+) 3

4 Chlorine = 7 electrons in outer shell Sodium = 1 electron in outer shell 7 e- in outer shell NaCl H 2 0 Pl Polar molecule l 1 e- in outer shell Oxygen = 6 electrons in outer shell Hydrogen = 1 electron in outer shell Ionic Bonding Covalent Bonding 46% oxygen (O 2- ) 28% silicon (Si 4+ ) 8% aluminum (Al 3+ ) 6% iron (Fe 2+ or Fe 3+ ) 4% magnesium (Mg 2+ ) 2.4% calcium (Ca 2+ ) 23% 2.3% potassium (K 1+ ) 2.1% sodium (Na 1+ ) Crystallization Slow cooling allows fewer (larger) crystals = coarse texture to rock These elements in a magma chamber bond and form minerals as the magma loses heat Rapid cooling leads to many small crystals = smooth texture to rock 4

5 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. (SiO4)4- Oxygen still needs 1 more electron each Single tetrahedron (SiO4)4Single chain (SiO3)2Double chain (Si4O11)6- Silicate sheet ((Si2O5)2- Silica tetrahedrons will form minerals with crystalline structure consisting of unlinked tetrahedra, chains, double chains, and sheets. Silicon tetrahedrons form chains (SiO3)2- Metallic cations fit inside the chains aluminum (Al3+) iron (Fe2+ or Fe3+) magnesium (Mg2+) calcium (Ca2+) potassium (K1+) ( ) sodium (Na1+) Three-dimensional Chains of silicates framework (Si3O8)4form because Oxygen bonds with Silicon a second time 5

6 Silicon tetrahedrons form chains (SiO3)2Cations move into spaces in silicate structures, but they will only form compounds that have no charge neutral (positive charges must equal negative charges) Single substitution Fe Must result in a neutral compound One cation may push another out of the latticework Mg Substitution Metallic cations fit inside the chains Na Pairs of cations that substitute for each other C Ca Double substitution Si aluminum (Al3+) iron (Fe2+ or Fe3+) magnesium (Mg2+) calcium (Ca2+) potassium (K1+) sodium (Na1+) Al Charge Size (nm) 46% oxygen (O2-) 2.3% potassium (K1+) % iron (Fe2+ or Fe3+) 4% magnesium (Mg2+) 28% silicon (Si4+) 8% aluminum (Al3+) 2.4% calcium (Ca2+) 2.1% sodium (Na1+) Atoms in a pair push each other outt off position 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. minerals Cation Substitution: Mineral must be neutral Na/Ca, Al/Si and Fe/Mg Olivine: single tetrahedron (SiO4)4[Fe22+(SiO4)4-] or [Mg22+(SiO4)4-] =0 or =0 Single Substitution Fe Mg Feldspar: 3-D framework (Si3O8)4[Na1+Al3+Si34+O82-]or [Ca2+Al23+Si24+O82-] =0 or =0 Double Na Substitution Al Ca Si 6