Mineral Identification Lab

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Mineral Identification Lab

• Purpose of Lab
• to observe the various physical properties of
  common rock forming minerals
• to utilize the combination of physical
  properties and determine the proper
  identification and chemical composition of
  common rock-forming minerals
• to understand that minerals make up rocks.

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Mineral Identification Lab

• What is a mineral???????
• Mineral Definition (5 parts)
• Naturally occurs
• Homogeneous solid
• Inorganic (non-living)
• Definite chemical composition
• Definite crystalline internal structure

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Mineral Identification Lab
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• Mineraloids (amorphous solid)
• Mineraloids are minerals that lack an internal
  atomic structure.
• Mineraloids do not have melting points.
• Examples
• What happens when one melts glass?
• Try melting plastic

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Physical properties of Minerals
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• Minerals are identified using physical
• properties. Mineral physical properties reflect
• the chemical composition and crystalline
• structure.
• Mineral Physical Properties
• crystal form
• color
• color of powdered residue
• reflection of light
• shape of the mineral
• hardness
• special mineral properties

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Physical Properties Mineral ID

• Crystal Form
• Crystal form represents flat well-defined
  smooth crystal faces that reflect the minerals
  internal atomic structure.
• Observation
• A mineral will show smooth flat surfaces
• or crystal faces that reflect a consistent
• angle between the faces for a particular
  mineral species.

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Various Crystal Forms
All quartz crystals, big, fat, skinny, will show
consistent angles between crystal faces.
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Physical Properties Mineral ID

• Color
• Color is the most noticeable physical property
  but the least accurate.
• The same mineral can occur in many different
  colors. Do not trust color.
• Observation
• A mineral can be red, green, blue, white,
  clear, smokey and many other colors.

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Different color fluorite minerals
Don't trust color
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Physical Properties Mineral ID

• Streak
• Streak is the Color of the powdered residue left
  on the porcelain streak plate.
• The mineral is scratched across the streak plate
  and the color of the powdered residue is
  observed.
• Some minerals show different color powder than
  the actual color of the mineral.
• Observation
• Observe the color of the powdered residue left
  on the porcelain streak plate.

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• Luster
• How does the mineral reflect light. Is the
  mineral metallic or non-metallic?
• Metallic Non-metallic
• resembles polished metal glossy
• vitreous (glassy)
• waxy, greasy
• earthy (concrete)
• resinous
• greasy
• pearly
• Observation
• Allow the light to reflect off the fresh mineral
  surface and determine if the mineral is metallic
  or non-metallic

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Incoming light waves
Very Very smooth surface
Very shiny
mineral surface
Incoming light waves
Smooth surface
shiny
mineral surface
Incoming light waves
Irregular surface
dull luster
mineral surface
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• Cleavage Planes
• Cleavage represents the tendency of a mineral to
  
• break in preferred directions along bright,
• reflective plane surfaces.
• A mineral will break along atomic planes of
• weakness, repeating the flat surfaces on
  smaller
• broken pieces.

Observation Look for the cleavage planes by
rotating the mineral and observing
flashing of light like turning on/off a
flashlight.
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Brakes along planes of weakness
Flashes of light (Checking for cleavage)
Cleavage surfaces
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• Fracture surfaces represent
• non-planer, non-parallel surfaces that reflect
  light in an uneven undulated fashion. When
  broken, smaller pieces will not repeat
  themselves.
• Example Once the crystal face is broken, the
  smooth flat surface will never again be
  observed.
• Observation
• Observe cracks, fractures, destruction on the
  flat surface as well as non-repeating flat
  surfaces. Notice the random or undulating
  reflective light as the mineral is rotated.

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Conchoidal fracture (dished shaped features)
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• Hardness
• How hard is the mineral or how the mineral
  resists scratching.
• German mineralogist Friedrich Moh (1773-1839)
  establishes mohs scale of hardness.
• Observation
• Does the mineral scratch glass?
• Yes the mineral is hard gt 7
• No mineral is lt 7

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Diamond
Softest
Scale of hardness not evenly distributed
Talc
Hardest
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Mohs Scale of Hardness
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• Special mineral properties
• Reaction to Acid Mineral will fizz when
  subjected to acid.
• Tenacity Mineral will bend (elastic).
• Striations Minerals display hairline grooves
  on crystal faces.
• Magnetism Magnets are attracted to the
  mineral.
• Double refraction An image beneath the
  mineral is repeated
• or doubled.
• Specific gravity How heavy is the mineral.
• Taste Does the mineral have taste??

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Acid reaction (fizzing)
Striations
Double Refraction
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• Mineral ID procedure
• Use the process of elimination or narrowing
  down the mineral name.
• Luster determine if the mineral is metallic or
  non-metallic
• Hardness Does the mineral scratch glass or not
  scratch glass?
• Cleavage planes does the mineral show cleavage
  or fracture?
• Use charts Use the mineral charts and narrow
  your field of choices to a select few.
  Carefully read the streak characteristics,
  color and any special physical properties
  select the proper name and indicate the
  chemical composition.

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