2.Why Study Minerals

8/7/2019 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.

2.Why Study Minerals

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