Download Minerals

Minerals
 Minerals are inorganic, naturally
occurring, homogenous, crystalline
substances.
– Crystal: A solid substance with atoms
arranged in an orderly, repeating pattern.
• Minerals are compounds of specific
elements (See your ESRT)
• A mineral can be composed of one
element, [i.e. graphite], or multiple
elements, [i.e. hornblende or augite.]
(See your ESRT – again!!)
In order for matter to be classified as a
mineral, it must meet these 5 requirements:
1.
2.
3.
4.
Occur naturally
Be a solid
Have a definite chemical composition
Have atoms arranged in an orderly pattern
[crystalline]
5. Be inorganic (not formed from plants,
animals, or other living organisms)
• Minerals occur whenever rocks are formed
since rocks are actually one or more
minerals grouped together to form an
aggregate.
• 99% of the Earth's crust is made up of only
eight elements. These are, in descending
order of volume, oxygen, potassium,
sodium, calcium, silicon, aluminum, iron,
and magnesium. These same elements
make up the majority of minerals. (Hmmm,
this might be in your ESRT . . .)
• Most rocks have a number of minerals in
common. Six of the most common rockforming minerals are: mica, olivine,
orthoclase [feldspar], plagioclase [feldspar],
pyroxene, and quartz.
• Mineral Identification:
Each mineral has
certain physical and
chemical properties
that can be used for
identification:
Color
• Color is not a good
property to be used in the
identification of minerals.
• It can be confusing
because some minerals'
colors are identical to other
minerals' colors. Many
minerals have different
colors caused by
impurities; quartz for
example, comes in a
myriad of colors  
Streak
• Streak is the color of the
powder of a mineral.
• It is closely related to
color, but is a different
property because the color
of the mineral may be
different than the color of
the streak. The streak is
more reliable because it
will be constant no matter
what impurities may be in
the mineral.
Luster
• Luster is the appearance of
light reflected off of the
surface of a mineral.
• The two main categories of
luster are metallic and
nonmetallic. Most minerals
are non-metallic. (ESRT!)
• A metallic luster shines, like
gold or steel [pyrite,
galena]
• A non-metallic luster can be
dull, glassy [like quartz], or
pearly [like hornblende]
Hardness
• Hardness is how well a substance will resist scratching by
another substance NOT an indication of how easily a
mineral breaks.
• The Mohs Scale is the standard scale to measure hardness.
It consists of numbers one through ten; 1 being the softest
(talc) and 10 being the hardest (diamond).
• Hardness is determined by comparing minerals to other,
known substances using the scale.
• Specific Gravity determines how heavy a
mineral is compared to an equal volume of
water.
• Water has a specific gravity of 1. If a mineral
has a specific gravity of 2.7, it is 2.7 times
heavier than water.
• Minerals with a specific gravity under 2 are
considered light, between 2 and 4.5 average,
and greater than 4.5 heavy.
• Most minerals with a metallic luster are
heavy. The specific gravity may vary slightly
within a mineral because of impurities present
in the mineral.
Cleavage is an indication of how a mineral
breaks and a mineral can break in two ways:
1.
Cleavage breaks
along flat surfaces.
2. Fracture breaks along
uneven surfaces and can be
demonstrated by irregular,
fibrous or curved edges.
• Chemical Properties determine the internal
arrangement of a mineral’s ions or atoms and
dictate the mineral’s characteristics.
• Diamond (left) and graphite (right) are both
composed of 100% carbon; the arrangment
of the atoms gives each its unique
characteristics.
• A crystal’s microscopic shape [the shape of its
internal atoms] will be reflected in its
macroscopic shape [the shape we see].
Mineral Identification:
• Minerals can be identified by observing the
characteristics discussed.
• ID kits contain a streak plate, hand lens, glass
plate, nail, and penny.
• Some minerals can be identified by observing
their reaction to an acid test. Calcite, for example,
will ‘fizz’ when it comes in contact with acid
(check your ESRT).
Mineral ID “Hints”:
• Useful properties:
– Hardness
– Cleavage/Fracture
– Specific Gravity
• Not-so Useful Properties:
– Color
– Luster
• All minerals are rocks. . .
• . . . but not all rocks are
minerals