Minerals
What is a Mineral?
• A naturally formed,
inorganic solid that
has a definite
crystalline shape.
•Made of elements and
two or more elements
chemically combined
called compounds.
How do minerals form?
1. Crystallization from magma
2. Precipitation
3. Pressure and temperature
4. Hydrothermal solutions
How are the mineral classified?
Are classified based on their chemical
composition.
1. Silicates
• Silicon and oxygen combine to form a structure
called the silicon-oxygen tetrahedron.
2. Nonsilicate
•Minerals that do not contain a combination of
silicon and oxygen.
-Six classes of nonsilicate minerals.
What are the nonsilicate mineral classes?
1. Native elements—minerals that are
composed of only one element.
2. Carbonates—minerals that contain
combinations of carbon and oxygen.
3. Halides—minerals that contain a halogen ion
plus one or more other elements.
4. Oxides—minerals that form when one or
more element combines with oxygen.
5. Sulfates—minerals that contain sulfur and
oxygen.
6. Sulfides—minerals that contain sulfur and
one or more element (excluding oxygen)
Over 2,000
are known!
How do we identify
minerals? Color
• Most easily
observed
property
• Yet, least
useful
property
Identifying Minerals: Color
It is the least useful
property because…
• 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
Mica Has Cleavage in One Direction
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, • 1. Talc
identified • 2. Gypsum
• 3. Calcite
numerically
• 4. Fluorite
by standard • 5. Apatite
minerals, • 6. Orthoclase
from 1 • 7. Quartz
(softest) to • 8. Topaz
10 (hardest): • 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
• 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