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Lecture Outlines PowerPoint
Chapter 2
Earth Science 11e
Tarbuck/Lutgens
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)
•Have a definite chemical composition (chemical formula)
•Possess an orderly internal structure of atoms
(A.K.A. crystal structure)
•Solid
•Inorganic (never living)
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?????
AtomsSmallest 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
__________ central part of an atom that contains • ___________ positive electrical charges • ___________ neutral electrical charges
Energy levels, or shells • Surround nucleus • Contain __________ negative electrical
charges
Nucleus
Protons
Neutrons
electrons
How atoms are constructed
_______ _________ is the number of protons in an atom's nucleus
Bonding of atoms • Forms a compound with two or more elements
• Ionic bonds and metalic bonds
• _______are atoms that gain or lose electrons
___________ Have varying number of neutrons and are radioactive
Atomic number
Ions
Isotopes
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 chamberAt, 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. Time
2. Space
3. Evaporation Rate
4. Dissolved Materials
5. Temperature
6. 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….
* (example: granite)
LARGE and well-formed
• If the magma cools quickly, then the crystals will….
*example: obsidian has a glass-like structure
Small / microscopic / not well-formed
Classzone Internet Investigation ES0506
“How Do Crystals Grow?”
2. Space
3. Evaporation rate
3. Amount of dissolved materials
3. Temperature
4. Pressurehttp://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
Figure 2.12
Mohs scale of hardness
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