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MINERALSSmith 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: Substance that cannot be broken down into other substances by ordinary chemical methods

ATOM: 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 MassNumber of Protons Determines the Atomic Number

● NEUTRONS No Charge and Contribute MassSame Size as Protons

● ELECTRONS- Charge and Contribute Tiny Percentage of MassMove 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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16P16N

STRUCTURE OF AN ATOMEX: SULFUR

ATOMIC NUMBER = 16

TOTAL NUMBER of ELECTRONS = 16

2 – INNER SHELL

8, 6 – OUTER SHELLS

Nucleus 16P16N

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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)StrongestAtoms share electrons with adjacent atoms

2. IONIC (see Figure 2.12, page 31)1 atom captures 1 or more electrons of another atomAtom 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 incompoundsand 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 alwaysdistributed 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 OXYGEN1 SILICON

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SILICATE STRUCTURES

3 OXYGEN 1 SILICON

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FERROMAGNESIAN (DARK) NON-FERROMAGNESIANSILICATES (LIGHT) SILICATES

OLIVINE MUSCOVITE

PYROXENE GROUP FELDSPAR

AMPHIBOLES QUARTZ

BIOTITE

GARNET

SILICATES(see Table 2.2, page 40)

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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 ionsMost common carbonates:

Calcite (CaCO3) – Reacts with hclDolomite (CaMg(CO3)2)

2. Other Oxide and Hydroxide MineralsIron oxides such as hematite (Fe2O3) and magnetite (Fe3O4)

3. Metallic MineralsGold (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