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Chapter 2
Earth Science 11e
Tarbuck/Lutgens
© 2006 Pearson Prentice Hall
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Earth Science, 11e
Minerals: Building
Blocks of Rocks
Chapter 2
Minerals are essential:
• They’re every manufactured product
• They’re essential to good health
• Knowledge of minerals enables us to understand
earth processes
Minerals: the building
blocks of rocks
Definition of a mineral: What are the 5
characteristics that make a mineral?
•Natural (found in nature)
•Solid
•Inorganic (never living)
•Possess an orderly internal structure of atoms
(A.K.A. crystal structure)
•Have a definite chemical composition (chemical formula)
Mineraloid - lacks an orderly internal structure
Composition and
structure of minerals
Elements
• Basic building blocks of minerals
• Over 100 are known
What is the #1 most abundant element in the
Earth’s crust?????
Atoms
Smallest particles of matter
Have all the characteristics of an element
Composition of continental crust
Figure 2.16
Periodic table of the Elements
Figure 2.4
Simplified view of the atom
Figure 2.5
How atoms are constructed
Nucleus
__________
central part of an atom that
contains
Protons
• ___________
positive electrical charges
Neutrons
• ___________
neutral electrical charges
Energy levels, or shells
• Surround nucleus
electrons
• Contain __________
negative electrical charges
How atoms are constructed
Atomic number
_______
_________ is the number of
protons in an atom's nucleus
Bonding of atoms
• Forms a compound with two or more elements
Ions
• Ionic bonds and metalic bonds
• _______are atoms that gain or lose electrons
Isotopes
___________
Have varying number of
neutrons and are radioactive
How atoms are constructed
Isotopes
• Have different mass numbers – the sum of the
neutrons plus protons
• Many isotopes are radioactive and emit energy
and particles
How minerals form:
1. Underground in the magma process
(most minerals)
2. Re-form deep within the earth in the
pressure process.
3. Near the surface in the evaporation (of
water) process
How Minerals form
•
The Magma Process:
1.
Molten (liquid) rock in a magma
chamber
At, near or under earth’s surface, rises
2. The magma begins to cool and atoms, ions and
molecules form various mineral compounds.
3. The molecules of the compounds mass together
to form crystals.
The Pressure Process:
1. Rock is exposed to high pressures and temperatures, and the
minerals begin to break down.
2. As pressure and temperature continue, the molecules RE-FORM
into new minerals.
3. The minerals are elongated in shape due to the pressure.
The Evaporation Process:
1. Ions (such as salt or calcium) are dissolved in water.
2. The water evaporates, and the ions form minerals
such as halite and calcite.
• Examples: halite (NaCl salt)
»
limestone (calcite)
Minerals
Physical properties of minerals
•
•
•
•
•
•
Crystal form
Luster
Color
Streak
Hardness
Cleavage
The mineral quartz often
exhibits good crystal form
Factors that determine crystal
formation:
1.
2.
3.
4.
5.
6.
Time
Space
Evaporation Rate
Dissolved Materials
Temperature
Pressure
Largest uncut diamond found in the Letseng Mine in
southern Africa. A near-flawless white gem weighing
nearly 500 carats. It was discovered on Sept. 8, 2008
It weighs 478 carats, with very few inclusions and of
outstanding color and clarity.
Mexico's Cueva de los Cristales (Cave of Crystals) contains some of the world's largest known natural
crystals—translucent beams of gypsum as long as 36 feet (11 meters).
Volcanic activity that began about 26 million years ago created Naica mountain and filled it with
high-temperature anhydrite gypsum. When magma underneath the mountain cooled and the
temperature dropped, the anhydrite began to dissolve and for millions of years have been deposited in
the caves in the form of huge selenite gypsum crystals.
1. TIME and mineral formation
The RATE at which
the molten magma
cools determines
the crystal size.
• If the magma has a lot of time and it cools
s-l-o-w-l-y then the crystals will….
LARGE and well-formed
* (example: granite)
• If the magma cools quickly, then the
crystals will….
Small / microscopic / not well-formed
*example: obsidian has a
glass-like structure
Classzone Internet Investigation
ES0506
“How Do Crystals Grow?”
2. Space
3. Evaporation rate
3. Amount of dissolved materials
3. Temperature
4. Pressure
http://www.classzone.com/books/earth_science/terc/content/investigations/es0506/
Summarize in a sentence:
So…. To grow the biggest, best synthetic
diamond crystal, you would….
time,
space,
cooling rate (temperature)
pressure
Pyrite (fool’s gold)
displays metallic luster
Figure 2.10
Mohs scale
of hardness
Figure 2.12
Minerals
Physical properties of minerals
• Fracture
• Specific gravity
• Other properties
•
•
•
•
Taste
Smell
Elasticity
Malleability
Minerals
Physical properties of minerals
• Other properties
•
•
•
•
•
Feel
Magnetism
Double Refraction
Reaction to hydrochloric acid
Fluorescence (UV)
Some rocks and minerals “glow”
under UV (black) light
Minerals
A few dozen minerals are called the rock-forming
minerals
• The eight elements that compose most rock-forming
minerals are…
• OXYGEN (O) (46.6% by weight)
• SILICON (Si), (27.7% by weight)
• aluminum (Al),
• iron (Fe),
• calcium (Ca),
• sodium (Na),
• potassium (K), and
• magnesium (Mg)
Composition of continental crust
Figure 2.16
??????
How can it be that…
oxygen (a gas) and
silicon (a metalloid) are
the #1 and #2 most abundant elements in
the earth’s crust?
Minerals
Mineral groups
• Most common Rock-forming mineral group is the:
Silicates
• Contain the silicon-oxygen tetrahedron (molecule)
• Four oxygen atoms surrounding a much smaller
silicon atom
Silicon-oxygen tetrahedron
(SiO4)-4 molecule
Figure 2.17
Minerals
Mineral groups
• Rock-forming silicates
• Combines with other atoms to form the various
silicate structures
• Groups based upon tetrahedral arrangement
• Olivine – independent tetrahedra
• Pyroxene group – tetrahedra are arranged in
chains
• Amphibole group – tetrahedra are arranged in
double chains
Minerals
Mineral groups
• Rock-forming silicates
• Groups based upon tetrahedral arrangement
• Micas – tetrahedra are arranged in sheets
• Two types of mica are biotite (dark) and
muscovite (light)
• Feldspars - Three-dimensional network of
tetrahedra
Hornblende – a member of
the amphibole group
Minerals
Mineral groups
• Rock-forming silicates
• Groups based upon tetrahedral arrangement
• Feldspars
• Two types of feldspar are Orthoclase and
Plagioclase
• Quartz – three-dimensional network of
tetrahedra
Three examples of perfect
cleavage – fluorite, halite,
and calcite
Conchoidal fracture
Figure 2.15
Potassium feldspar
Plagioclase feldspar
Minerals
Mineral groups
• Rock-forming silicates
• Feldspars are the most plentiful mineral group
• Crystallize from molten material
• Nonsilicate minerals
• Major groups
• Oxides
• Sulfides
Minerals
Mineral groups
• Nonsilicate minerals
• Major groups
• Sulfates
• Carbonates
• “Native” elements
Native Copper
Minerals
Mineral groups
• Nonsilicate minerals
• Carbonates
• A major rock-forming group
• Found in the rocks limestone and marble
• Halite and gypsum are found in sedimentary rocks
• Many have economic value
Minerals
Mineral resources
• Reserves are already identified deposits
• Ores are useful metallic minerals that can be
mined at a profit
• Economic factors may change and influence a
resource
An underground halite (salt) mine
Mineral Gemstones
• A gemstone is defined as…
Precious? semi-precious?
Tumbled “Gems” Stones
Gems are valued for their reflective properties due to
the way they cut (facets).
Topaz
• Rough – uncut – unpolished
Malachite
• Raw form
cut and polished
Turquoise
• Natural turquoise
jewelry
Opal
• Raw form
End of Chapter 2