Download Minerals - Frost Middle School

Minerals
Characteristics of
minerals
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Naturally forming
Solid
Has a definite chemical makeup
Has a crystal structure
Inorganic
How are minerals
grouped
• Based on their chemical makeup
• Silicates most common
o Contain oxygen and silicon
o Make up 90% of the rocks in Earth’s crust
o Quartz
o Feldspar
o Mica
How are minerals
grouped continued
• Carbonates
o Another group common in rocks
o Contain carbon and oxygen
o React with HCL (Hydrochloric Acid)
o Calcite
• Oxides
o Do not form rocks
o From where most metals are refined from
o When an element (metal) joins with oxygen
Properties to help identify
a mineral
1. Color
a. Three factors that determine color
• Tiny amounts of an element that is not part of
the normal chemical makeup
o Pure Quartz is clear and colorless but tiny
amounts of iron make it violet – Called
amethyst
• Can change when it is at or near Earth’s
surface verses in contact with the
atmosphere or water
• May have defects in their crystal structure
that change the color
Properties to help identify
a mineral
2. Streak
a. Color of the powder left behind when
the mineral is scraped across a surface
b. Streak plates used to determine the color
c. Better clue to the identity than surface
color
d. All samples of the same mineral will have
the same streak color
Properties to help identify
a mineral
3. Luster
a. The way light reflects from its surface
b. Metallic
• Looks like it was made of metal
c. Nonmetallic
• Does not look like its made of metal
d. Can very from sample to sample – just like color
e. If the mineral is broken it will reveal its
characteristic luster
Properties to help identify
a mineral
4. Cleavage
a. The tendency of a mineral to break along flat
surfaces
b. Depends on how the atoms are bonded
together
• Crystal structure is weaker in the direction in
which the mineral breaks
c. Both the direction and smoothness of the
broken surface are considered
Properties to help identify
a mineral
5. Fracture
a.Tendency of a mineral to
break into irregular pieces
b.Bonds that join the atoms
are fairly equal in strength in
all directions
Properties to help identify
a mineral
6. Density
a.Very helpful in identifying the
mineral
b.Every mineral has its own
density no matter what the
sample size is
Properties to help identify
a mineral
7. Hardness
a. The resistance to being
scratched
b. Mohs Scale
c. Minerals can scratch another
mineral of the same hardness or
softer
Some special properties of
minerals
• Carbonic minerals react with hydrochloric
acid
• Fluorescence
o Glow when exposed to ultraviolet light
o Fluorite &calcite
o Not very helpful
o Some samples of the same element might
or might not have the property
Some special properties of
minerals
• Magnetic
o Magnets are pulled toward the mineral
o Magnetite is strongly magnetic
• Radioactive
o Contain unstable elements that change into
other elements over time
o This releases energy
• This energy is measured to identify the mineral
• Uraninite, Autunite, Uranopilite, and
Andersonite