2.Why Study Minerals
Transcript of 2.Why Study Minerals
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Why StudyWhy Study
Minerals?Minerals?Minerals are the way atoms areMinerals are the way atoms are
arranged in rocks.arranged in rocks. Atomic environments in rock are Atomic environments in rock arehomogeneous from the mm scale tohomogeneous from the mm scale tothe scale (7 orders of magnitude).the scale (7 orders of magnitude).
1 = 101 = 10--1010
m = 10m = 10--77
mmmm Mineralogy is solid Mineralogy is solid--statestategeochemistry.geochemistry.
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Minerals are fundamental to EarthSciences.
Environmental sciences
Geochemsitry
Geophysics
Mineralogy is a mature science.
Mineralogy is primarily a tool for
understanding the Earth
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Definition of a MineralDefinition of a Mineral
A mineral is a naturally occurring,homogeneous solid with a definite,
but not fixed, composition, and anordered atomic arrangement that isformed by inorganic processes.
A mineral is a natural, crystalline
phase.
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Minerals are NaturallyMinerals are NaturallyOccurringOccurring
In order to be a mineral, a chemicalcompound must occur naturally
somewhere and be stable enough tostudy in the lab.
We can make many compounds inthe lab that are not minerals unless
they are found in nature.
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Mineral are homogeneousMineral are homogeneous
Minerals are chemicallyhomogeneous down to the atomic
scale.
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Definite, but not fixed,Definite, but not fixed,composition.composition.
Minerals have chemical formulasdetermined by the atomic structures.
Symmetry requires atoms to occur insimple, specific, integer ratios.
But, for a given mineral,substitutions of similar elements arepossible.
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Ordered atomicOrdered atomicarrangementarrangement
Minerals are crystals (crystallinesolids).
Crystals are periodic arrays of atoms. Atoms achieve their lowest energy
by having each different type ofatom (element) in an identicalenvironment.
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Ordered atomicOrdered atomicarrangementarrangement
Halite (NaCl) Fluorite (CaF2)
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Inorganic ProcessesInorganic Processes
The mineral must have at least oneoccurrence where it is formed byinorganic processes.
Calcite may be formed by organismsto form shells, but it also occurs inigneous and metamorphic
environments.
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These are MineralsThese are Minerals
Gold, silver, diamond, graphite
Pyrite, marcasite, sphalerite
Salt (halite), fluorite, calcite, Apatite Olivine, garnet, zircon
Pyroxene, amphibole, mica, Quartz,
feldspar, zeolite
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Polymorphs and IsomorphsPolymorphs and Isomorphs
Polymorph:
same composition, different structure
Isomorph:
same structure, different composition
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Polymorphs
Two minerals with the same composition, butdifferent structures are different minerals.
Diamond and graphite are both pure carbon, butare different minerals
Quartz-tridymite-cristobalite-coesitestishovite:
all polymorphs of SiO2.
Calcite and aragonite are CaCO3.
This is why we use mineral names rather thanchemical formulas.
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Isomorphs
Minerals with the same structure
and different compositions are isomorphs.
Forsterite (Mg2SiO4)- fayalite (Fe2SiO4) Halite (NaCl) - sylvite (KCl), periclase (MgO),
galena (PbS)
Gold (Au) - silver (Ag)
Quartz (SiO2) - berlinite (AlPO4)
Muscovite-Biotite
Sometimes theres crystalline solution,sometimes not.
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TUGAS 2TUGAS 2
Buat resume tentang definisimineral, isomorf dan polimorf.
Cari literatur lain yang berhubungandengan tugas 2.