Download Minerals of the Earth’s Crust

Minerals of the
Earth’s Crust
Chapter 9
Mineral: a naturally occurring
substance formed in the Earth
• Inorganic
• Always a
crystalline
solid
• Definite
chemical composition
Over 2,000
are known!
Identifying Minerals:
Color
• Most easily
observed
property
• Yet, least
useful
property
Identifying Minerals: Color
Why it is the least useful
property…
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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
Identifying Minerals:
Luster
•Way a
mineral
shines in
reflected
light
Identifying Minerals: Luster
Metallic:
shines like polished metal
Pyrite
“Fool’s
Gold”
Identifying Minerals: Luster
Nonmetallic:
does not shine like metal
Identifying Minerals: Luster
Pearly
like a
pearl
Talc
Identifying Minerals: Luster
Greasy
Turquoise
Identifying Minerals: Luster
Vitreous
like
shining
glass
Amethyst
Identifying Minerals: Luster
Resinous
like wax
Identifying Minerals: Luster
Dull or
Earthy
Bauxite
Identifying Minerals:
Crystal Shape
•The shape of a crystal
results from the way
the atoms of a mineral
come together as the
mineral forms
Identifying Minerals:
Streak Test
• Color of a mineral’s
powder form
• Usually, streak is not the
same color as the mineral
• Streak doesn’t vary
Identifying Minerals:
Streak Test
• Metallic mineral has
dark streak
• Nonmetallic – colorless
or light streak
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
Identifying Minerals:
Cleavage
Identifying Minerals:
Fracture
• the way a mineral
tends to break
Identifying Minerals:
Fracture
Splintery
jagged
Identifying Minerals:
Hardness
•Resistance to being
scratched
•Moh’s hardness scale
• Mohs Scale,
identified
numerically
by standard
minerals,
from 1
(softest) to
10 (hardest):
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1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond
To remember the Mohs scale
try remembering this phrase:
The Geologist Can Find
An Ordinary Quartz,
(that) Tourists Call
Diamond!
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:
Tools for Testing
Hardness
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finger nail (H = 2.5)
penny (H = 3.5)
common nail (H = 4.5)
glass plate (H = 5.5)
Identifying Minerals:
Special Properties
•Acid
test
http://www.westhamptonbe
ach.k12.ny.us/Teachers/Co
hen/sciweb/earthscience/s
edimentary/Mvc-327w.mpg
Identifying Minerals:
Special Properties
•Magnetic
test
Identifying Minerals:
Special Properties
•Taste test
Some minerals have a distinct
taste. Never do this test
after the acid test!
Quartz
Feldspar
Mica
Talc
Amphiboles
Galena
Halite
Biotite
Calcite
Hematite
Pyrite
Magnitie
Olivine
Garnets