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Lecture 3 - Mineralogy PowerPoint PPT Presentation


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Lecture 3 - Mineralogy. http://www.soest.hawaii.edu/coasts/gg101/index.html. 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

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Lecture 3 - Mineralogy

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Lecture 3 - Mineralogy

http://www.soest.hawaii.edu/coasts/gg101/index.html


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, 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. ???


Hawaii’s most common mineral – volcanic Olivine

Hawaii’s second most common

mineral – marine Calcite


How are minerals built?


Review the

structure of

an atom


Structure of the Atom -

8

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


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


How are minerals built?


Octet Rule


Chlorine = 7 electrons in outer shell

Sodium = 1 electron in outer shell

NaCl

7 e- in outer shell

1 e- in outer

shell

Ionic Bonding


H20

Polar molecule

Oxygen = 6 electrons in outer shell

Hydrogen = 1 electron in outer shell

Covalent Bonding


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


Crystallization

Slow cooling allows fewer (larger)

crystals = coarse texture to rock

Rapid cooling leads to many small

crystals = smooth texture to rock


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.

(SiO4)4-

Oxygen still needs 1 more electron each


Silica tetrahedrons will form

minerals with crystalline structure

consisting of unlinked tetrahedra,

chains, double chains, and sheets.


Single tetrahedron

(SiO4)4-

Single chain

(SiO3)2-

Double chain

(Si4O11)6-

Silicate sheet

(Si2O5)2-

Three-dimensional

framework

Chains of silicates

form because Oxygen bonds with Silicon a second time

(Si3O8)4-


Silicon tetrahedrons form chains

(SiO3)2-

Metallic cations fit inside the chains

aluminum (Al3+)

iron (Fe2+ or Fe3+)

magnesium (Mg2+)

calcium (Ca2+)

potassium (K1+)

sodium (Na1+)


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

other


Must result in a

neutral compound

Silicon tetrahedrons form chains

(SiO3)2-

One cation may

push another out of the

latticework

Single substitution

Fe

Mg

Substitution

Metallic cations fit inside the chains

aluminum (Al3+)

iron (Fe2+ or Fe3+)

magnesium (Mg2+)

calcium (Ca2+)

potassium (K1+)

sodium (Na1+)

Na

Ca

Double substitution

Si

Al


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

position

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

Single

Substitution

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


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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