Prentice Hall EARTH SCIENCE

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Prentice Hall EARTH SCIENCE

• Tarbuck Lutgens

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Chapter 2
Minerals
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2.1 Matter
? Elements are the basic building blocks of
minerals.

• Over 116 elements are known, 90 occur in nature.
• An element is a substance that cannot be broken
  down into simpler substances by chemical or
  physical means.

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2.1 Matter
? Smallest particles of matter
? Have all the characteristics of an element
? The nucleus is the central part of an atom and
contains

• protons, which have positive electrical charges

• neutrons, which have neutral electrical charges

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2.1 Matter
? Energy levels, or shells

• surround the nucleus

• contain electronsnegatively charged particles

• The atomic number is the number of protons in the
  nucleus of an atom. The atomic number identifies
  the element.
• Ex. All atoms of carbon have the atomic number 6
  because they all have 6 protons.

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Model of an Atom
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2.1 Matter
? Isotopes of an element have the same number of
protons but varying numbers of neutrons.
? Have different mass numbers the sum of the
neutrons plus protons is the total mass of the
atom in atomic mass units.
? Many isotopes are radioactive and emit energy
and particles in a process called radioactive
decay.
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2.1 Matter
? When an atoms outermost energy level does not
contain the maximum number of electrons (8,
except for H, Li, Be), the atom is likely to form
a chemical bond with one or more atoms.

• A compound consists of two or more elements that
  are chemically combined in specific proportions.

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2.1 Matter
Chemical bonds are the forces that hold atoms
together in a compound. There are three principal
types
1. Ionic bonds form between positive and negative
ions. An ion is an atom that has gained or lost 1
or more electrons, has a charge. These
compounds are called salts
2. Covalent bonds form when atoms share electrons.
3. Metallic bonds form when metal ions share a
sea of electrons.
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2.2 Minerals
1. Naturally occurring
2. Generally considered inorganic

• 3. Solid substance

4. Orderly crystalline structure
5. Definite chemical composition
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2.2 Minerals
1. Crystallization from magma
2. Precipitation
3. Pressure and temperature
4. Hydrothermal solutions
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Minerals Formed as a Result of Crystallization of
Magma
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How minerals form

• Magma is molten rock from deep in the Earth. As
  it cools, it forms minerals.
• Substances dissolved in water may react to form
  minerals.
• Changes in temperature and pressure can make
  new minerals form.
• When hot solutions touch existing minerals,
  chemical reactions take place and form new
  minerals. Takes place in or near hydrothermal
  vents on the ocean floor.

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2.2 Minerals
? Can be classified into 6 groups based on their
composition
1. Silicates

• Silicon and oxygen combine to form a structure
  called the silicon-oxygen tetrahedron. This
  silicon-oxygen tetrahedron provides the framework
  of every silicate mineral.

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The Silicon-Oxygen Tetrahedron
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Silicon-Oxygen Chains, Sheets, and
Three-Dimensional Networks
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• Silicates are made of silicon and oxygen.
• They are the most common group of minerals on
  Earth.
• Most silicate minerals crystallize from cooling
  magma.

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• quartz

kaolin
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2.2 Minerals
2. Carbonates

• Minerals that contain the elements carbon,
  oxygen, and one or more other metallic elements

3. Oxides

• Minerals that contain oxygen and one or more
  other elements, which are usually metals

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2.2 Minerals
4. Sulfates and Sulfides

• Minerals that contain the element sulfur

5. Halides

• Minerals that contain a halogen ion plus one or
  more other elements

6. Native elements

• Minerals that exist in relatively pure form

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Sulfides
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Native Copper
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2.3 Properties of Minerals
? Small amounts of different elements can give
the same mineral different colors.
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2.3 Properties of Minerals
? Streak is the color of a mineral in its
powdered form.
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2.3 Properties of Minerals
? Luster is used to describe how light is
reflected from the surface of a mineral.
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Pyrite (Fools Gold) Displays Metallic Luster.
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2.3 Properties of Minerals
? Crystal form is the visible expression of a
minerals internal arrangement of atoms.
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Quartz Often Exhibits Good Crystal Form.
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2.3 Properties of Minerals
? Hardness is a measure of the resistance of a
mineral to being scratched.
? Mohs scale consists of 10 minerals arranged
from 10 (hardest) to 1 (softest).
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Mohs Scale of Hardness
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2.3 Properties of Minerals
? Cleavage is the tendency of a mineral to
cleave, or break, along flat, even surfaces.
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Mica Has Cleavage in One Direction
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2.3 Properties of Minerals
? Minerals that do not show cleavage when broken
are said to fracture.
? Fracturethe uneven breakage of a mineral
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Conchoidal Fracture
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2.3 Properties of Minerals
? Density is a property of all matter that is
the ratio of an objects mass to its volume.
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2.3 Properties of Minerals
? Some minerals can be recognized by other
distinctive properties.