Download Mineral Identification Lab

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
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
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 mineral’s 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
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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
resembles polished metal
Non-metallic
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 moh’s scale of hardness.
Observation:
Does the mineral scratch glass?
Yes – the mineral is hard > 7
No – mineral is < 7
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Diamond
Softest
Scale of hardness
not evenly distributed
Talc
Hardest
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Moh’s 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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