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Lecture 3 - Mineralogy PowerPoint PPT Presentation

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Lecture 3 - Mineralogy. Atoms build . Earth’s Crust. Molecules build. Rocks build. Minerals build. Bingham Copper Mine – copper, silver, gold, molybdenum. What is a Mineral?. A mineral is a naturally occurring , inorganic solid - PowerPoint PPT Presentation

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Lecture 3 - Mineralogy

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Lecture 3 - Mineralogy

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Atoms build



Molecules build

Rocks build

Minerals build

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Bingham Copper Mine – copper, silver, gold, molybdenum

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What is a Mineral?

A mineral is a naturally

occurring, inorganicsolid

with an orderly internal

arrangement of atoms

(called crystalline structure)

and a definite, but sometimes

variable, chemical composition

Page: 28[FCS1]Source?

Page: 28[FCS2]According to Gloss of Geol, “used in mfr of glass, enamel, HF acid; steel not mentioned. ???

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Hawaii’s most common mineral – volcanic Olivine

Hawaii’s second most common

mineral – marine Calcite

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How are minerals built?

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Review the

structure of

an atom

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Structure of the Atom -


If we drew a hydrogen atom to scale, making the nucleus

the diameter of a pencil, the electron would orbit about

0.5 km from the nucleus. The whole atom would be the size

of a baseball stadium…with so much empty space, how can

our world feel so solid?

Octet Rule…filled outer orbital

Atomic Number…number of protons

Mass Number…number of protons and neutrons

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Isotopes of an atom have variable

number of neutrons (mass number)

Most atoms exist in a charged

state due to the need to have

a filled outer shell - Ions

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How are minerals built?

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Octet Rule

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Chlorine = 7 electrons in outer shell

Sodium = 1 electron in outer shell


7 e- in outer shell

1 e- in outer


Ionic Bonding

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Polar molecule

Oxygen = 6 electrons in outer shell

Hydrogen = 1 electron in outer shell

Covalent Bonding

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46% oxygen (O2-)

28% silicon (Si4+)

8% aluminum (Al3+)

6% iron (Fe2+ or Fe3+)

4% magnesium (Mg2+)

2.4% calcium (Ca2+)

2.3% potassium (K1+)

2.1% sodium (Na1+)

These elements in a magma

chamber bond and form

minerals as the magma loses heat

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Slow cooling allows fewer (larger)

crystals = coarse texture to rock

Rapid cooling leads to many small

crystals = smooth texture to rock

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Most abundant elements? – silicon and oxygen

Silicon has 4 electrons in outer shell

= needs 4 more.

Oxygen has 6 electrons in outer shell

= needs 2 more.


Oxygen still needs 1 more electron each

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Silica tetrahedrons will form

minerals with crystalline structure

consisting of unlinked tetrahedra,

chains, double chains, and sheets.

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Single tetrahedron


Single chain


Double chain


Silicate sheet




Chains of silicates

form because Oxygen bonds with Silicon a second time


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Silicon tetrahedrons form chains


Metallic cations fit inside the chains

aluminum (Al3+)

iron (Fe2+ or Fe3+)

magnesium (Mg2+)

calcium (Ca2+)

potassium (K1+)

sodium (Na1+)

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Cations move into spaces in

silicate structures, but

they will only form compounds

that have no charge – neutral

(positive charges must

equal negative charges)

Pairs of cations that

substitute for each


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Must result in a

neutral compound

Silicon tetrahedrons form chains


One cation may

push another out of the


Single substitution




Metallic cations fit inside the chains

aluminum (Al3+)

iron (Fe2+ or Fe3+)

magnesium (Mg2+)

calcium (Ca2+)

potassium (K1+)

sodium (Na1+)



Double substitution



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Charge Size (nm)

46% oxygen (O2-) 0.132

2.3% potassium (K1+) 0.133

6% iron (Fe2+ or Fe3+) 0.064

4% magnesium (Mg2+) 0.066

28% silicon (Si4+) 0.042

8% aluminum (Al3+) 0.050

2.4% calcium (Ca2+) 0.099

2.1% sodium (Na1+) 0.097

Atoms in

a pair push

each other

out of


Cation Substitution: Mineral must be neutral

Na/Ca, Al/Si and Fe/Mg

Olivine: single tetrahedron (SiO4)4-

[Fe22+(SiO4)4-] or [Mg22+(SiO4)4-]

+4 +4 –8=0 or +4 +4 –8=0



Fe Mg

Feldspar: 3-D framework (Si3O8)4-

[Na1+Al3+Si34+O82-]or [Ca2+Al23+Si24+O82-]

+1 +3 +12 –16=0 or +2 +6 +8 –16=0

Double Na Ca

Substitution Al Si

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As the Si and O build crystalline structures and the metallic cations play single and double substitution, the entire magma chamber grows into a solid mass of minerals….

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