MINERALS

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MINERALS
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• What is a mineral?
• How do we differentiate a mineral from a piece of
  wood or a human?
• What is a rock?

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Minerals

• What is a mineral?
• Naturally occurring (not man-made)
• Inorganic
• Crystalline Solid (interlocked pattern of
  molecules)
• Definite chemical structure which give it unique
  physical properties.
• Ex. Diamonds

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Minerals vs. Rocks

• There are nearly 4000 known minerals - but most
  rocks are formed by only a few dozen minerals.
• Rocks are aggregates (mixtures) of minerals. So .
  . . minerals are the building blocks of rocks.
• Question
• How do minerals come together to form a rock?

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Composition and Structure of Minerals

• To understand how minerals form, we need to
  understand the characteristics of elements and
  atoms.
• Elements are the basic building blocks of
  minerals. There are over 100 known elements.
• Atoms are the smallest particle of matter that
  exhibits all the characteristics of an element.

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Composition and Structure of Minerals

• Atoms are made up of
• Nucleus, which contains
• Protons- positive electrical charges
• Neutrons - no charge
• Shells which surround the nucleus and contain
  Electrons - negative electrical charges
• The mass (density) of an element depends on the
  number of protons and neutrons in the nucleus.

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Combining Elements to Form Minerals

• Elements combine with each other to form a wide
  variety of minerals.
• The new mineral (compound) will have very
  different physical properties from the elements
  that combined to form it.
• Ex 1 Calcium
• 1 Carbon CaCO3
• 3 Oxygen

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Combining Elements to Form Minerals

• Since rocks are mixtures (not chemical
  combinations) of minerals, minerals keep their
  physical properties within a rock.
• Question Is it possible for two different
  minerals to have the same chemical composition?
• YES! Both diamond and graphite are made of
  carbon. The difference between these two
  minerals is the way in which the carbon atoms are
  arranged.

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Rock Forming Minerals

• The most common rock forming minerals are
  composed of 8 elements
• Oxygen (O)
• Silicon (Si)
• Aluminum (Al)
• Calcium (Ca)
• Sodium (Na)
• Potassium (K)
• Iron (Fe) and Magnesium (Mg)
• There are just a few dozen minerals that we call
  the rock-forming minerals.

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Silicate Minerals

• Silicate minerals
• Contain both silicon (Si) and oxygen (O)
• The most common rock-forming minerals
• May contain one or more other elements
• Silicates make up 96 of the Earths crust.

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Silicate Mineral Groups

• Feldspars form depending on which metal
  combines with the Si O atoms
• Two common types of feldspars
• Orthoclase (K, Al)
• Plagioclase (Ca, Na)
• Most plentiful mineral group
• Quartz composed ONLY of Si O atoms
• ( NO other elements )

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Silicate Minerals
Biotite
Quartz
Muscovite
Plagioclase Feldspar
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Non-Silicate Minerals

• Major groups Contain no Silicon
• Oxides (metal O) Ex. Hematite, magnetite
• Sulfides (metal S) Ex. Pyrite fools gold,
  galena
• Sulfates (S O) Ex. Gypsum plaster
• Halides Ex. Halites salt
• "Native" elements (dont combine with any other
  elements) Ex. Gold, silver, carbon, copper
• Carbonates (C O) Ex. limestone, marble
• Non-Silicates make up 4 of the Earths crust.

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Non-Silicate Minerals
Pyrite
Hematite
Halite (salt)
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Non-Silicate Minerals
Gold
Flourite
Galena
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Mineral Properties

• Minerals have lots of different properties that
  help us identify them
• Crystal form -set of faces that have a definite
  geometric relationship to one another.
• Luster metallic or nonmetallic shine
• Color
• Streak minerals color in powdered form
• Hardness Mohs hardness scale/scratch resistance
  of one mineral against another
• Cleavage how it breaks along preferred planes
• Fracture no preferred plane (no flat surface)
• Specific gravity -describes the density of the
  mineral
• Taste, Smell, Fluorescence etc.

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Identifying Minerals

• Color can help with mineral identification.
• Color of the mineral
• Color of the streak on a porcelain plate
• Example Hematite is gray in color and has a red
  streak

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Identifying Minerals

• Luster shiny or dull
• Luster - the way a mineral reflects light
• Look for luster on a fresh surface.
• The three major types of luster are
• metallic,
• glassy (vitreous)
• and dull.

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Name
Cleavage how mineral breaks
Plane
Basal
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Prismatic
2
3
Cubic
Rhombo- hedral
3
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(a) cubic (b) 12-sided (c) octahedral (d)
hexagonal
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Identifying Minerals

• Most minerals (except metals) have one or more
  cleavage planes that also help in determining
  their identity.
• Cleavage Plane A region where a rock cleanly
  splits
• Occur in areas of weak bonds between atoms and
  molecules.
• Mica has 1 cleavage plane
• Halite has 3 cleavage planes

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Mohs hardness scale

• 1. Talc 7. Quartz
• 2. Gypsum/fingernail 8. Topaz
• 3. Calcite/penny 9. Corundum
• 4. Fluorite 10. Diamond
• 5. Apatite
• 6. Potassium Feldspar/steel nail

Scratch one mineral against another to see how
resistant it is.
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Material Mohs hardness scale
Streak plate 7
Glass plate 5.5 - 6
Nail 4
Copper/Penny 3
Fingernail 2
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Mineral Identification

• Common items to test for hardness
• A fingernail (2.5) will scratch gypsum and be
  scratched by calcite
• A penny (3) is scratched by fluorite
• Glass (5.5- 6) scratches apatite and is scratched
  by orthoclase (a feldspar)