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MINERALS. Chemical composition of the Crust. Oxygen most abundant- 46.6% Followed by silicon and aluminum Iron, Calcium, Sodium, Potassium, Magnesium The most common minerals will be composed mostly of these elements Silica & silicates. MINERAL vs. ROCK. ROCK
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Chemical composition of the Crust • Oxygen most abundant- 46.6% • Followed by silicon and aluminum • Iron, Calcium, Sodium, Potassium, Magnesium • The most common minerals will be composed mostly of these elements • Silica & silicates
MINERAL vs. ROCK • ROCK • An aggregate of one or more MINERALS (usually- coal, organic) • MINERAL • Solid • Crystalline- orderly arrangement of atoms • Naturally occurring • Inorganic • Definite chemical composition • e.g. SiO2 for quartz; KAlSi3O8 for feldspar
Atom & Elements • Atoms • Neutral • Nucleus • Proton, neutron • Electron • Ions • Electrical Charge • Molecule- e.g. water molecule
Chemical activity • Stable atoms want • positive & negative charges balanced • electron shells full • Ions- positive (Cations) and negative (Anions) • Bonding • Ionic • Covalent • Metallic • Van der Waal’s
Element • Atomic number • Number of PROTONS • Isotope • Differing number of NEUTRONS • Atomic weight • Mass of PROTONS and NEUTRONS
Crystallinity • 3 dimensional orderliness of atoms • Silicon-oxygen tetrahedron • Silicate structures • Single- e.g. olivine • Chain • Single chain- pyroxene • Double chain- amphibole • Sheet- e.g. mica, clay • Framework- e.g. quartz, feldspar
MINERALS • Crystalline solids • Natural and Inorganic Substances • Definite chemical composition • Can be written as a chemical formula • Solid solution (within a range)
Important Minerals • Quartz (most abundant) • FELDSPAR Group • Potassium Feldspar - Orthoclase • Plagioclase Feldspar • Sodium (Na) Albite • Calcium (Ca) Anorthosite
Important Minerals • PYROXENE Group- Augite most common • AMPHIBOLE Group- Hornblende most common • MICA Group- Si + O in sheets • Biotite • Muscovite • CALCITE- CaCO3
Properties of Minerals • Color • Not always reliable (Olivine, green; Flourite, yellow, purple, green…) • Ferromagnesian minerals green or black • Streak- powdered form • Luster- reflectance of light • Metallic • Nonmetallic • Vitreous or Glassy • Earthy
Properties of Minerals • Hardness- resistance to scratching • Moh’s Hardness Scale • Fingernail = 2.5 • Penny = 3.5 • Knife/Glass = 5.5 • Streak Plate= 6.5 • Crystal Form • Law of Constancy of Interfacial Angles
Properties of Minerals • Cleavage • Quality (poor, good, perfect) • Number of directions • One- e.g. Mica • Two at right angles- e.g. Feldspar, Pyroxene • Two not at right angles- e.g. Amphibole • Three at right angles (cubic)- e.g. Halite • Three not at right angles (rhombohedral)- e.g. calcite • Four (Flourite) or six (Sphalerite)- not common
Properties of Minerals • Fracture • Absence of cleavage • Irregular fracture • Conchoidal fracture- Quartz • Density • Specific Gravity • Some unusual properties • Striations, Magnetism, Taste, Odor, Double refraction
Chemical tests • Reaction with HCl • Calcite effervesces
ROCK CYCLE • Equilibrium • Interrelationships between • igneous rocks • sediment • sedimentary rocks • metamorphic rocks • weathering and erosion • Plate Tectonic Example
ROCK CYCLE • Equilibrium • Interrelationships between • igneous rocks • sediment • sedimentary rocks • metamorphic rocks • weathering and erosion • Plate Tectonic Example