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MINERALS MINERAL vs. ROCK • ROCK z An aggregate of MINERALS (usually) • MINERAL z Crystalline- orderly arrangement of atoms z Naturally occurring z Inorganic z Definite chemical composition z e.g. SiO2 for quartz; KAlSi3O8 for feldspar Atoms & Elements • Atoms z Nucleus z Proton, neutron z Electron • Molecule- e.g. water molecule • • • Atomic number Isotope Atomic weight Element Chemical activity • Stable atoms want z positive & negative charges balanced z electron shells full • Ions • Bonding z Ionic z Covalent z Metallic Chemical composition of the Crust • Oxygen most abundant • Followed by silicon and aluminum • The most common minerals will be composed mostly of these elements • Silica & silicates Crystallinity • 3 dimensional orderliness of atoms • Silicon-oxygen tetrahedron • Silicate structures z Isolated- e.g. olivine z Chain z Single chain- pyroxene z Double chain- amphibole z (asbestos) z Sheet- e.g. mica, clay z Framework- e.g. quartz, feldspar MINERALS • Crystalline solids • Natural] Substances • Specific chemical composition z Can be written as a chemical formula z Solid solution z Zoning Important Minerals • • • • • • • • • • • • • Quartz FELDSPAR Group z Potassium Feldspar z Plagioclase Feldspar z Sodium (Na) , Calcium (Ca) Feldspar PYROXENE Group- Augite most common AMPHIBOLE Group- Hornblende most common MICA Group- Si + O in sheets z Biotite z Muscovite CALCITE- CaCO3 Properties of Minerals Color z Not always reliable z Ferromagnesian minerals green or black Streak Luster z Metallic z Nonmetallic z Vitreous or Glassy z Earthy Hardness Moh’s Hardness Scale z Fingernail = 2.5 z Penny = 3.5 z Knife/Glass = 5.5 Crystal Form z Law of Constancy of Interfacial Angles Cleavage z Quality z Number of directions z One- e.g. Mica z Two at right angles- e.g. Feldspar, Pyroxene z Two not at right angles- e.g. Amphibole z Three at right angles (cubic)- e.g. Halite z Three not at right angles (rhombohedral)- e.g. calcite Four or six- not common Fracture z Absence of cleavage z Irregular fracture z Conchoidal fracture Density z Specific Gravity Some unusual properties z Striations, Magnetism, Taste, Double refraction Chemical tests Reaction with dilute HCl z Calcite effervesces Minerals you need to identify Feldspar z Al silicate with Na, K, Ca Quartz z SiO2 “Ferromagnesian minerals” z Silicates with Fe & Mg Micas z Sheet silicates (biotite or muscovite) Calcite CaCO3 z z • • • • • • • • • ROCK CYCLE • Interrelationships between z igneous rocks z sediment z sedimentary rocks z metamorphic rocks z weathering and erosion • Plate Tectonic Example
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