Minerals of the Earths Crust

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Minerals of the Earths Crust

• Chapter 9

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Mineral a naturally occurring substance formed
in the Earth

• Inorganic
• Always a crystalline solid
• Definite chemical composition

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Over 2,000 are known!
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Identifying Minerals Color

• Most easily observed property
• Yet, least useful property

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Identifying Minerals ColorWhy it is the least
useful property

• Different minerals have the same color
• One mineral can have different colors
• Impurities can alter color
• Some change color when exposed to air
• Way a mineral shines in reflected light distorts
  color

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Identifying Minerals Luster

• Way a mineral shines in reflected light

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Identifying Minerals Luster

• Metallic
• shines like polished metal

Pyrite Fools Gold
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Identifying Minerals Luster

• Nonmetallic
• does not shine like metal

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Identifying Minerals Luster

• Pearly
• like a pearl

Talc
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Identifying Minerals Luster

• Greasy

Turquoise
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Identifying Minerals Luster

• Vitreous
• like shining glass

Amethyst
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Identifying Minerals Luster

• Resinous
• like wax

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Identifying Minerals Luster

• Dull or Earthy

Bauxite
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Identifying Minerals Crystal Shape

• The shape of a crystal results from the way the
  atoms of a mineral come together as the mineral
  forms

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Identifying Minerals Streak Test

• Color of a minerals powder form
• Usually, streak is not the same color as the
  mineral
• Streak doesnt vary

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Identifying Minerals Streak Test

• Metallic mineral has dark streak
• Nonmetallic colorless or light streak

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Identifying Minerals Cleavage

• The splitting of a mineral along certain flat
  surfaces
• Related to the types of bonds in the internal
  structure of the mineral

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Identifying Minerals Cleavage
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Identifying Minerals Fracture

• the way a mineral tends to break

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Identifying Minerals Fracture
jagged
Splintery
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Identifying Minerals Hardness

• Resistance to being scratched
• Mohs hardness scale

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• Mohs Scale, identified numerically by standard
  minerals, from 1 (softest) to 10 (hardest)

• 1. Talc
• 2. Gypsum
• 3. Calcite
• 4. Fluorite
• 5. Apatite
• 6. Orthoclase
• 7. Quartz
• 8. Topaz
• 9. Corundum
• 10. Diamond

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To remember the Mohs scale try remembering this
phrase

• The Geologist Can Find An Ordinary Quartz,
  (that) Tourists Call Diamond!

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Tools for Testing Hardness

• You typically do not carry around a supply of the
  10 minerals on the hardness scale. However, you
  can use the following items to help estimate the
  hardness of a mineral

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Tools for Testing Hardness

• finger nail (H 2.5)
• penny (H 3.5)
• common nail (H 4.5)
• glass plate (H 5.5)

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Identifying Minerals Special Properties

• Acid test

http//www.westhamptonbeach.k12.ny.us/Teachers/Coh
en/sciweb/earthscience/sedimentary/Mvc-327w.mpg
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Identifying Minerals Special Properties

• Magnetic test

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Identifying Minerals Special Properties

• Taste test

Some minerals have a distinct taste. Never do
this test after the acid test!
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Common Rock-forming Minerals
Quartz
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Feldspar
Mica
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Talc
Amphiboles
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Galena
Halite
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Biotite
Calcite
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Hematite
Pyrite
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Magnitie
Olivine
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Garnets