Download Minerals

Lecture 3: Minerals
Geol 101, J.S. Kite
WVU, 2009
GEOL 102 Announcement:
• Bring manual to lab EVERY week
Mineral
7naturally occuring,
solid inorganic
element or
compound of
elements, …..
Spodumene
Specimen from John Betts: www.johnbetts-fineminerals.com/index.htm
Mineral
7naturally occuring, solid inorganic element
or compound of elements,
with a definite composition, or range
of compositions,
usually having regular
internal crystalline
structure.
Watermelon Tourmaline
has range in composition
Objective for Today
• Explain how chemistry works to
form different mineral crystals
with different properties.
properties.
• Example: carbon crystals
– diamond vs. graphite
Sources of Carbon Images
Diamond
by Joel Castellanos, ©1998
www.cs.unm.edu/~joel/CrystalLab/CrystalLab.html
Graphite
www.auburn.edu/~leeming/ graphite.jpg
Physical Properties of Minerals
• Chemical Composition
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Crystal Structure
Cleavage
Fracture
Hardness
Specific Gravity
Color
Streak
Lustre
Chemical Composition
• Assume Some Chemistry Background, p.
32-38, Plummer & others, 2007, 11th ed.
• Know Terms Like
– Atomic Number
– Atomic Weight ?H.S. Chemistry?
• ~ atomic mass number
– Electron, Proton, Neutron, Isotope, etc.
• Symbols Textbook, Appendix C, p. A-7
Elements
Building Blocks for Minerals,
(Minerals Building Blocks for Rocks).
Rocks).
• 92 Natural Elements in the
Universe (see Appendix D p. AA-8)
• 99% of Universe is H, He
Whole Earth
Most Common Elements?
• Fe (35% by weight or mass)
• O (30%)
• Si + Mg + Ni + 87 other
elements = ~ 35 %
Elements in Earth’s crust
O = 47 % by wt.; 94 % by volume
Si = 28 % by wt.; <1% by volume
Al, Fe, Ca, Na, K, Mg: 2-8% each)
Rest ~ 1.5% total
(See p. 38 in Plummer & others, 2007)
2 Models
of the
Atom
Most elements occur as ions.
• Ions:
Ions: Atoms with Unbalanced
Number of Protons (+) &
Electrons ((-)
• Valence:
Valence: Combining Capacity
e.g. H2O
H+ & H+ & O-2
• Cation (+ charged ion)
• Anion ((- charged ion)
Atoms of
Two “Inert”
Elements
Electron # =
Proton #
Valence:
Valence:
Combining
Capacity
H2 O
Molecule
Chemical Composition
• Most Properties are
Determined by Chemistry
• Minerals Classified by
Chemistry
• Read Textbook:
Textbook: p. 3333-43 in
Plummer & others, 2007)
Mineral Classes
• Silicates (SiO4)-4
Quartz (SiO2), Garnets,
Micas, Feldspars
• Other Mineral Groups
Quartz
Garnet
– Oxides
O-2
– Sulfides
S-4
– Carbonates (CO3)-2
– Halides
Cl-
• Mineraloids
– Lack “xl” structure
Images from John Betts: www.johnbetts-fineminerals.com/index.htm
K-Feldspar & Quartz
Mineral Classes
• Silicates (SiO4)-4
• Oxides O-2
–Hematite (Fe2O3) & Limonite:
Iron Oxide (Rust)
•
•
•
•
•
Sulfides S-4
Carbonates (CO3)-2
Halides ClOther Mineral Groups
Mineraloids
Matt Goff’s Toyota Pickup
www.nawwal.org/~mrgoff/pictures/
misc/pickup2.jpg
Mineral Classes
• Silicates
(SiO4)-4
• Oxides O-2
• Sulfides S-4
–Pyrite (FeS2):
=Fool’s Gold
•
•
•
•
Carbonates (CO3)-2
Halides ClOther Mineral Groups
Mineraloids
Mineral Classes
• Silicates (SiO4)-4
• Oxides O-2
• Sulfides S-4
• Carbonates (CO3)-2
–Calcite (CaCO3)
Calcite
Image from John Betts: www.johnbetts-fineminerals.com/index.htm
Mineral Classes
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•
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•
Silicates (SiO4)-4
Oxides
O-2
Sulfides
S-4
Carbonates (CO3)-2
• Halides Cl- Br- Fl- etc.
–Halite (NaCl): Rock Salt
• Other Mineral Groups
• Mineraloids
Mineral Classes
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•
•
•
•
Silicates (SiO4)-4
Oxides
O-2
Sulfides S-4
Carbonates (CO3)-2
Halides
Cl-
• Other Mineral Groups
– Weird Stuff
Image from John Betts:
• Mineraloids
www.johnbettsfineminerals.com/index.htm
Mineral Classes
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Silicates
(SiO4)-4
Oxides O-2
Sulfides
S-4
Carbonates (CO3)-2
Halides ClOther Mineral Groups
• Mineraloids
–No Xline Structure
–e.g. Opal, Agate
Agate
Physical Properties of Minerals
• Chemical Composition
• Crystal Structure
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Cleavage
Fracture
Hardness
Specific Gravity
Color
Streak
Lustre
Valence & Size of
Combining Atoms
Determine a Mineral’s
Crystal Structure
Crystal (xl)
• Solid with an Orderly
Atomic Arrangement,
• Which May Develop
External Faces that Give
the Crystal Form
Halite (NaCl)
Crystal Lattice
• 3D Arrangement of Atoms within a Mineral
Galena
Crystal
Lattice
Unit Cell
• Smallest Unit of 3D Arrangement for a Mineral
Types of Bonds,
p. 36 in Plummer et al. 2007 Textbook
Ionic
+ or - Valence Attraction
Carbon in 2 forms:
diamond w/ covalent
bonds, graphite w/ van
der Walls bonds
Types of Bonds,
p. 36 in Plummer et al. 2007 Textbook
Ionic
+ or - Valence Attraction
Covalent
Shared Electrons
Metallic
Free Electrons
Carbon in 2 forms:
diamond w/ covalent
bonds, graphite w/ van
der Walls bonds
Van Der Waals (not in book):
book):
Weak Electrostatic Attraction
Quartz
Amethyst
Cut Amethyst
(Quartz)
Maine Geological Survey
Amethyst Images Source:
Maine Geological Survey
Si Tetrahedral Layers (SiO2)
Triangular Pyramid
Si4+ in Center
O2- at Nodes
#
Slides Marked with # Were Taken
In Part From This Web Site:
An Insiders Look at the Silicates
Natural History Museum of Los Angeles County
http://www.nhm.org/lacmnh/departments/
research/mineralogy/silicates/index.htm
Si Tetrahedral Layers (SiO2)
#
Minerals
Olivine,
Garnets
Silicate
Groups
See Textbook
p. 38-39
Pyroxenes
Amphiboles
Micas,
Clays
Quartz,
Feldspars
Structure
Al(OH)3 or Al Octahedron
Al
OH-
#
Van Der Waals Bonds on Sheet Sillicate
Physical Properties of Minerals
• Chemical Composition
• Crystal Structure
• Cleavage
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Fracture
Hardness
Specific Gravity
Color
Streak
Lustre
Cleavage
• Tendency for a
Mineral to Break
Along a Plane of
Weakness
Van Der Waals Bonds in Mica
Cleavage:
Flourite & Feldspar
Physical Properties of Minerals
• Chemical Composition
• Crystal Structure
• Cleavage
• Fracture
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Hardness
Specific Gravity
Color
Streak
Lustre
Fracture
ƒ Any Breaking Not Along a
Plane of Weakness
Conchoidal
Fracture in
Malachite
Physical Properties of Minerals
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Chemical Composition
Crystal Structure
Cleavage
Fracture
• Hardness = Scratchability
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Specific Gravity
Color
Streak
Lustre
Mohs
(1822)
Hardness
Scale
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Talc
Gypsum
Calcite
Fluorite
Apatite
Orthoclase
Quartz
Topaz
Corundum
Diamond
Hardness Scale
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•
fingernail = 2.5
copper penny = 3.5
pocket knife = 5.5
glass = 5.5
steel file = 6.5
Physical Properties of Minerals
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Chemical Composition
Crystal Structure
Cleavage
Fracture
Hardness
• Specific Gravity
• Color
• Streak
• Lustre
Specific Gravity
Mineral
Mass/Volume
g/cm3
water
1.000
ice
0.917
most minerals 2.0 to 4.0
galena
7.5
gold
19.3
Physical Properties of Minerals
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Chemical Composition
Crystal Structure
Cleavage
Fracture
Hardness
Specific Gravity
• Color
• Streak
• Lustre
Color
• Obvious for Few Minerals
• Inconsistent
• Minor Atomic Substitutions Give
Great Variety of Color to One
Mineral
Quartz = Amethest
Corundum = Ruby
Physical Properties of Minerals
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Chemical Composition
Crystal Structure
Cleavage
Fracture
Hardness
Specific Gravity
Color
• Streak
• Lustre
STREAK
COLOR OF POWDER
MORE CONSISTENT
THAN CRYSTAL
COLOR
Hematite: Reddish Brown Streak
Physical Properties of Minerals
•
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Chemical Composition
Crystal Structure
Cleavage
Fracture
Hardness
Specific Gravity
Color
Streak
• Lustre
Lustre
•
Metallic
• Nonmetallic
– Dull
– Glassy
– Pearly
– Adamantine
Other Physical Properties
Specific to Few Minerals,
may be Diagnostic
Calcite:
- ExamplesNormal Light
¾Magnetism
¾Reaction to HCl
¾Fluorescence
(UV Light)
Calcite:
UV Light
Rock
solid cohesive
aggregate of grains of
one or more minerals.