Transcript Unit 2: Minerals

Minerals
Minerals are…..
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Naturally occurring
Inorganic
Solid
Composed of elements or
compounds
• Elements are composed
of only one type of atom.
• Compounds are 2 or
more elements
chemically combined
Physical Characteristics...
• Are the result
of the
arrangement
of atoms
within the
mineral.
Physical Characteristics include...
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Color
Luster
Fracture and cleavage
Mineral shape (habit)
Streak
Hardness
Specific Gravity
Color
• Color of some
minerals is a very
useful characteristic
to use in identifying
them. This sulfur for
example is almost
always yellow.
However, color can be altered by
the presence of small amounts of
chemical impurities, so…...
• Color should not be
relied on too heavily
as an identifying
characteristic for
most minerals. Agate
shows that quartz can
occur in many
different colors, for
example.
• Luster is the way
in which a mineral
reflects, refracts,
or absorbs
light….in other
words the way
that it shines.
Luster may be
“Metallic”...
Or it may be “non-metallic”.
• Non-metallic mineral
lusters include such
descriptions as
earthy, pearly, glassy,
dull, or silky.
• is the way in which
a mineral breaks.
If the mineral
breaks along
smooth flat
surfaces like
calcite or mica, it is
said to cleave.
• Fracture refers to the
characteristic of
breaking along rough
irregular surfaces.
Mineral like quartz
are said to
“fracture”. Think of
a meat cleaver and a
bone fracture to keep
these terms straight.
Crystal shape
• The shape of a
mineral crystal is
determined by the
arrangement of its
atoms. Each
mineral tends to
occur in a limited
number of crystal
shapes.
• Streak is the color
of the powder left
behind when the
mineral is rubbed
on a piece of
unglazed
porcelain.
• Hardness is a
mineral’s resistance to
being scratched.
• A numerical scale
from 1-10 is used to
measure hardness.
(Moh’s Scale)
• Talc is the softest
mineral at #1.
• Diamond is hardest
• Specific gravity is the
ratio of a mineral’s
mass compared to an
equal volume of
water. In other
words, how many
times heavier is the
mineral than the
same amount of
water?
Determining Specific Gravity
• Determine the mass of the mineral
• Suspend the mineral in a beaker of water
and redetermine its mass
• Find how much mass was lost when the
mineral was suspended in water.
• Divide the mass in air by the amount of
mass lost when suspended in water
• Answer = specific gravity
Common Mineral Groups...
• Silicates •
The 2 most abundant
elements in the earth’s
crust are oxygen and
silicon.
• These combine to form
an atomic structure
called a tetrahedron.
• These tetrahedra form
minerals called silicates.
• A group of minerals in
which carbon and
oxygen combine to
form a carbonate CO3
molecule.
• The test for these is
the bubble test. When
exposed to
hydrochloric acid they
release CO2 and they
bubble.