Lecture'8''Patterns'in'Nature:'Minerals'Minerals'• The'“building'blocks”'of'rocks,'and'hence,'of'Earth.'• More'than'4,000'are'known'• New'minerals'are'discovered'annually'• Developed'societies'depend'on'mineral'resources'• Economically'important'–drives'world'economies''• Historically'important'–dictated'human'history'What'is'a'Mineral?'• Naturally'occurring''• Solid'• Crystalline'–orderly'internal'structure''atoms'arranged'in'a'definite'pattern'• Definite'Chemical'composition''Definition'of'Mineral'• A'mineral'is'a'naturally'occurring'solid'with'a'highly'ordered'atomic'arrangement'and'definite'(but'not'fixed)'chemical'composition.'It'is'usually'formed'by'inorganic'processes'Rocks'• Rocks'are'Earth'material'made'from'minerals''• Most'rocks'have'more'than'one'kind'of'mineral'• Some'are'monomineralic'Chemical'Concepts'• Element:'substance'that'cannot'be'separate'into'other'elements'• Atom:'smallest'particle'of'an'element'that'retains'chemical'properties''• Nucleus:'core'of'atom'containing'protons'and'neutrons'• Subatomic'particles:'Neutrons'–electrically'neutral'subatomic'particle'Protons'–positively'charged'subatomic'particle'Electrons'–negatively'charged'subatomic'particle''Atomic'number=number'of'protons'in'nucleus'• Number'of'protons'unique'to'each'element'Atomic'weight~number'of'protons'plus'number'of'neutrons'Isotopes'are'atoms'of'the'same'element'with'differing'numbers'of'neutrons'Ions''• When'an'element'has'the'same'number'of'protons'and'electrons,'it'is'neutral'(w/'no'charge)'• Unequal'number'of'electron'and'protons'a'net'electrical'charge'an'ion'Bonding'Molecule'(or'compound):'two'or'more'atoms'bonded'together'Bond:'interaction'between'two'or'more'atoms'that'holds'them'together'The'type'and'strength'of'bonding'govern'mineral'properties'5'recognized'types'of'bonds'• Covalent'–sharing'of'electrons''• Ionic'–bond'between'a'metal'and'a'non'metal'• Metallic'–sharing'of'free'electrons'among'a'lattice'of'metal'atoms'atoms'in'“sea”'of'electronshigh'conductively''• Van'der'Waals'–a'secondary'interatomic'bond'between'adjacent'molecular'dipoles''• Hydrogen'–the'attractive'interaction'of'a'hydrogen'atom'with'an'electronegative'atom'that'comes'from'another'molecule'Polymorphs'• Same'composition'but'different'crystal'structure'• Diamond'and'graphite'are'carbon'polymorphs'Mineral'Physical'Properties'• Characteristics'determined'by'your'5'senses'• Used'to'ID'minerals'• Properties'depend'upon…'• Chemical'composition'• Crystal'structure'• Some'are'diagnostic'• Minerals'have'a'unique'set'of'physical'properties''Color'• Color'is'diagnostic'fro'some'minerals'• Some'minerals'may'exhibit'a'broad'color'range'• Color'varieties'often'reflect'trace'impurities''Streak'• Color'of'a'mineral'crushed'on'unglazed'porcelain'• Streak'is'often'diagnostic'property'Hardness'• Scratching'resistance'of'a'mineral'• Hardness'compared'to'the'Mohs'Hardness'Scale'Luster'• Is'it'dull'or'reflected'Specific'Gravity'• Related'to'density'(mass'per'volume)'• Mineral'weight'over'weight'of'equal'water'volume'• Specific'gravity'is'“heft”'–how'heavy'it'feels'• Pyrite'“feels”'heavier'then'feldspar'Crystal'Habit'• Crystal'habit:'shape'of'a'single'well'formed'crystal''• Crystal'habit'is'the'ideal'shape'of'crystal'faces'• Ideal'growth'requires'ideal'conditions'many'terms'are'used'to'describe'habit'Crystal'Form'• Minerals'vary'in'crystal'face'development''• Euhedral'crystal'–a'crystal'displaying'well`formed'faces'• Anhedral'crystal'–a'crystal'without'well'formed'faces'• Anhedral'crystals'are'more'common'than'Euhedral'Cleavage'•
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