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Unit 2 Chapter 5


Unit 2 Chapter 5 Minerals of Earth's Crust Minerals: Are naturally occurring, inorganic solid that has a definite chemical composition with the atoms arranged in an ... – PowerPoint PPT presentation

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Title: Unit 2 Chapter 5

Unit 2 Chapter 5
  • Minerals of Earth's Crust

Minerals Are naturally occurring, inorganic
solid that has a definite chemical composition
with the atoms arranged in an orderly pattern.
  • Characteristics of Minerals
  • There are 4 characteristics that the object must
    fit into
  • Is it organic?
  • Does it occur naturally?
  • Is it a crystalline solid?
  • Does it have a definite chemical composition?

Kinds of Minerals
  • There are approximately 4000 known minerals
  • Approximately 20 of the minerals are called rock
    forming and approximately 90 makes up the
    earth's crust. 90 of the minerals are a
    combination of the common elements. The rest of
    the minerals are rare or in rare quantities.

Silicate Minerals   Silicate A mineral that
contains a combination of silicon and
oxygen. Most common minerals that make up
approx 95 of the earth's crust Common ones
include quartz and the feldspars (rocksandmineral
  • Non Silicate Minerals
  • Carbonates
  • Contain carbon
  • Halides
  • Chlorine, fluorine combined with sodium,
    potassium or calcium
  • Native Elements
  • Composed of a single element
  • Gold - Au
  • Silver - Ag
  • Sulfur - S
  • Diamond - C
  • Oxides
  • Contain Oxygen and other elements
  • Sulfates
  • Contain sulfate (SO4) and other elements

Crystalline Structure
  • Crystal
  • Atoms that are arranged in a regular repeating
  • Can be seen with your eye, microscope or x-ray

Crystalline Structure of Silicate Minerals
  • Silicon-Oxygen Tetrahedron
  • Basic building block of rocks in the earth's
  • 4 Oxygen
  • 1 Silicon
  • Hint - know this name and this shape it may come
    up again!!!!
  •  Hornblende - Silicon Tetrahedrons form the shape
    of a chain.
  • - Oxygen will bond with Si to form a bumpy
  • Mica - Si tetrahedrons form a flat sheet
  •  Pyroxene- Si tetrahedrons form a chain

Section 2 Identifying Minerals
  • Mineralogy
  • The study of minerals
  • Mineralogist
  • The scientist who studies minerals

Physical properties of Minerals
  • Color -
  • Easy to determine but not too good because many
    minerals have the same color
  • Also many minerals may have more than one color.
  • Reasons 1. impurities may change color
  • 2. Air may change color
  • 3. Many different minerals may have the same

Streak Test
  • By using an unglazed white tile and rubbing the
    mineral over the tile it can produce a powder.
    Each mineral's streak is always the same color no
    matter what the color of the mineral is.

  • Metallic - looks and shines like a metal
  • Non metallic - can be shiny but does not look
    like a metal

Cleavage and Fracture  
  • Cleavage
  • The tendency of a mineral to split easily or
    separate along flat surfaces.
  • Ex. Mica - one directional perfect cleavage
  • Fracture -
  • The mineral breaks along a surface that is not a
    cleavage surface.
  • 1c. Conchoidal -shell like fracture
  • Ex. Obsidian
  • 2c. Fibrous - splintery - produces jagged, sharp
  • Ex. Copper
  • 3c. Uneven or irregular - generally rough

Hardness - It is the resistance to being
scratched. If a mineral scratches another
mineral it is harder than the other mineral.  
  • Moh's Hardness Scale
  • Uses objects easily found with earlier
  • 1. Finger Nails
  • 2. Copper penny (prior to 1975)
  • 3. Steel (knife)
  • 4. Glass (watch or glasses)

The scale Mohs (mineralogist, 1773-1839) scale is
used mostly. Rosiwal shows cutting strength and
Vickers shows denting strength.
  • It is a shape only easily observed with large

  • Ratio of mass of a substance to the volume of the
  • Density Mass
  • Volume
  • Specific Gravity Simple definition
  • The objects weight in air verses its weight in
    water (compares densities)  

Special Properties
  • Fluorescence - the ability to glow under Ultra
    violet light
  • Phosphorescence - the ability to glow after
    lights are turned off
  • Double Refraction - 2 images can be seen through
    the mineral
  • Ex. Calcite
  • Magnetism - minerals can be picked up or is
    attracted to a magnet.
  • Ex. Magnetite
  • Radioactivity -the ability to release energy and
    activate a Geiger counter
  • Ex. Uranium

Another way to determine a mineral
  • Acid Test
  • Weak acids can cause calcite to fizz (bubble)
    like putting water on an "Alka Seltzer" tablet.

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