6. Minerals and Rocks

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6. Minerals and Rocks

• 6.1 Minerals are all around us
• 6.2 Rocks form in different ways
• 6.3 Natural processes break down rocks
• 6.4 Geologic maps show Earths surface features

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6.1 Minerals are all around us

• Before, you learned
• Earth is made of layers
• Earths outermost rocky layer is the crust
• Now, you will learn
• About the characteristics of minerals
• How minerals are classified into groups
• Which mineral group in most common

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Warm-up Questions

• Latitude is a distance in degrees ________ or
  _________ of the _________
• (T/F) Relief maps use contour lines to show
  features
• Geographic information systems display data in
  _____ to build maps

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Minerals and rocks are part of daily life

• Wires carrying eletric current are made of copper
  a mineral!
• Table salt (halite) a mineral!
• The Earths crust is made of rocks almost all
  rocks are made of minerals!

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Minerals

• Minerals are not the same as rocks
• A rock has only two of the characteristics
• Solid and forms in nature
• A rock usually has two or more types of minerals
• Minerals are always made up of the same materials
  in the same proportions
• Quartz crystal has 2 Oxygen atoms for every
  silicon atom

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Minerals

• A mineral is (generally) an inorganic, naturally
  occurring, organized crystalline structure
  composed of a single chemical compound or
  element.
• A rock is (generally) a natural solid composed of
  multiple crystals of one or more minerals
• Although many rocks contain visible crystals of
  individual minerals, a rock itself does not have
  an overall crystalline structure.

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Minerals have four characteristics
" A naturally occurring, inorganic material of
constant chemical composition and a definite
crystalline structure."

• 1. Form in nature
• 2. Are solids
• 3. Have a definite chemical makeup
• 4. Have a crystal structure
• Examples copper in the wires that carry
  electricity, table salt (halite)
• Is water a mineral? Is ice?
• Can minerals be found in rocks?

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Minerals 1. Formed in Nature

• Can be formed by processes that do not
  necessarily involve living organisms
• A few minerals can be produced by organisms as
  part of shells or bones
• Haline forms when water evaporates in a hot
  shallow part of the ocean
• Granite forms when molten
• rock cools

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Minerals 2. Solids

• Definite volume and a rigid shape
• Volume amount of space an object takes up

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Minerals 3. Definite Chemical Makeup

• Specific combination of atoms of certain elements
• Element a substance that contains only one type
  of atom
• Atom is the smallest particle an element can be
  divided into
• Most minerals contains more than one element
  compounds elements in specific proportions

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Halite NaCl
Copper - Cu
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Minerals 4. Have a Crystal Structure

• Crystal solid in which the atoms are arranged in
  an orderly, repeating 3-D pattern
• Two minerals can have the same chemical
  composition but different crystal structures

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• Diamond and graphite are both made of Carbon
• The individual atoms have the same properties,
  but are in different arrangement giving the
  substance very different properties different
  crystal structure

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Minerals are grouped according to composition

• Grouped on the basis of chemical makeups
• Most common group is silicates
• Contain oxygen silicon most common in Earths
  crust joined together
• Rock-forming minerals
• The 30 minerals that make up most of the crust
• Silicates make up 90 of the rocks in the crust
• Quartz, feldspare, and mica
• 2nd most common Carbonates (carbon and oxygen) -
  calcite

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Rocks are made of minerals

• Minerals
• must have the four previously mentioned
  characteristics
• Always made of the same elements in the same
  proportions, have an orderly crystal structure
• A rock only has two of the four
• It is a solid and forms naturally
• Rocks are usually made of two or more minerals
• The proportion of different minerals in a certain
  type of rock may vary
• The minerals in a rock can be all jumbled
  together
• Only a few types of rocks are made of only one
  type of mineral
• Ex limestone (calcite)
• A few contain no minerals at all
• Ex obsidian (made of natural glass no crystal
  structure)
• Ex Coal (remains of ancient plants)

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Math in Science

• Each mineral makes up a certain proportion, or
  fraction, of a granite sample
• You can compare mineral amounts by expressing
  each minerals fraction as a percentage
• To change a fraction to a percentage, you must
  find an equivalent fraction with 100 as the
  denominator
• 1/5 to percent?
• First, divide 100 by the denominator 5 20
• Then multiply the numerator and denominator by 20
  20/100 20

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Minerals in a Granite Sample
Mineral Fraction of granite sample Percentage of granite
quartz 1/4
feldspar 13/20
mica 3/50
Dark minerals 1/25