Download MINERALS Smith and Pun – Chapter 2

MINERALS
Smith and Pun – Chapter 2
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ATOMIC STRUCTURE
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ATOMIC STRUCTURE (2)
(See Smith and Pun, pages 29-35)
ELEMENT:
ATOM:
Substance that cannot be broken
down into other substances by
ordinary chemical methods
Smallest possible particle of an element
that retains the properties of that
element
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ATOMIC STRUCTURE (3)
ATOMS COMPOSED OF 3 SUBATOMIC PARTICLES:
● PROTONS
+ Charge and Contribute Mass
Number of Protons Determines the Atomic Number
● NEUTRONS
No Charge and Contribute Mass
Same Size as Protons
● ELECTRONS
- Charge and Contribute Tiny Percentage of Mass
Move Rapidly Around Nucleus in Pathways Called
Shells or Orbitals
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ATOMIC STRUCTURE (4)
ISOTOPE: Atoms containing the same number of
protons but a different number of
neutrons
The most common isotope of oxygen (O2) has 8
neutrons; the isotope of O2 with 10 neutrons is far
less abundant.
Radioactive isotopes are important in determining
the age of rocks.
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STRUCTURE OF AN ATOM
EX: SULFUR
ATOMIC NUMBER = 16
TOTAL NUMBER of ELECTRONS = 16
2 – INNER SHELL
8, 6 – OUTER SHELLS
Nucleus
16P
16P
16N
16N
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CHEMICAL BONDS
Atoms tend to react with other atoms when the outermost
shell is only partially filled.
Electrons like to be paired.
The reactions that occur result in the formation of chemical
bonds.
1. COVALENT (see Figure 2.13, page 32)
Strongest
Atoms share electrons with adjacent atoms
2. IONIC (see Figure 2.12, page 31)
1 atom captures 1 or more electrons of another atom
Atom that loses electron (cation) +
Atom that gains electron (anion) -
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CHEMICAL BONDS (2)
3.
HYDROGEN BONDS (see Figure 2.15, page 32)
Weak bond formed between hydrogen atoms incompounds
and strong electronegative atoms in other molecules
Hydrogen bonding between ice and water molecules affects
the structure of water giving it unique properties
4.
van der WAALs BONDS
Weak bond formed because electrons are not always
distributed equally around atoms or molecules. The
irregular distribution of electrons means that a weak
negative charge may exist on the side with more electrons,
and a weak positive charge on the side with a deficiency of
electrons.
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Minerals are composed of an ordered array of atoms
chemically bonded together to form a particular crystalline
structure.
POLYMORPH – Minerals with the same chemical
composition but different physical properties
Ex: diamond and graphite (pencil lead)
Both are composed of carbon (C) but diamond forms under
conditions of very high pressure.
Graphite consist of widely spaced sheets of carbon atoms
loosely held together.
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CRYSTAL STRUCTURE OF DIAMOND
(see Figure 2.23, page 37)
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CRYSTAL STRUCTURE OF GRAPHITE
(see Figure 2.23, page 37)
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MINERAL IDENTIFICATION
(see text pages 24-29 and Table 2.1, page 28)
CRYSTAL FORM – Are crystal faces well developed?
LUSTER – Character of light reflected by mineral
COLOR
STREAK – Color of mineral in powdered form
HARDNESS – Resistance of mineral to scratching
CLEAVAGE – Tendency to break along smooth planes
FRACTURE - Minerals that do not break along cleavage
planes, fracture
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CLEAVAGE
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CONCHOIDAL FRACTURE
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MINERAL IDENTIFICATION (2)
SPECIFIC GRAVITY - Ratio of the weight of a mineral to the
weight of an equal volume of water
TASTE
HCL –Carbonates will fizz (CO2 gas is being formed)
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MINERAL GROUPS
(see Figure 2.24, page 39)
Approximately 10 minerals are abundant in earth’s crust or
common rock forming minerals.
Rock forming minerals generally consist of about 8 elements.
2 most abundant elements:
● Silicon (Si)
● Oxygen (O)
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MAJOR MINERAL GROUPS
SILICATES – Minerals contain silicon and oxygen
As well as 1 or more other elements
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SILICON OXYGEN TETRAHEDRON
4 OXYGEN
1 SILICON
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SILICATE STRUCTURES
3 OXYGEN
1 SILICON
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SILICATES
(see Table 2.2, page 40)
FERROMAGNESIAN (DARK)
SILICATES
NON-FERROMAGNESIAN
(LIGHT) SILICATES
OLIVINE
MUSCOVITE
PYROXENE GROUP
FELDSPAR
AMPHIBOLES
QUARTZ
BIOTITE
GARNET
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GARNET
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ASBESTOS
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NON-SILICATE MINERALS
1. Carbonates
Carbonate ion and 1 or more positive ions
Most common carbonates:
Calcite (CaCO3) – Reacts with hcl
Dolomite (CaMg(CO3)2)
2. Other Oxide and Hydroxide Minerals
Iron oxides such as hematite (Fe2O3) and magnetite (Fe3O4)
3. Metallic Minerals
Gold (Au) and Copper (Cu) are two examples
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KARAT VS. CARAT
KARAT – PURITY OF
GOLD (24 KARATS)
CARAT – UNIT OF
WEIGHT FOR
PRECIOUS GEMS
1 CARAT =0.2 GRAMS
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