Download Mineral ID lecture - Holden R

What is a Mineral?
A mineral must occur naturally in the Earth’s crust. It cannot be
a manufactured or manmade item.
A mineral must be inorganic rather than organic. Organic
materials are formed from living things.
A mineral is always a solid. Minerals cannot be liquids or gases.
A mineral has a definite chemical composition. Minerals may be
made of a single element. Some minerals are formed by
compounds, or combinations of two or more elements.
A mineral’s atoms are arranged in a definite pattern. This
repeating patter is called a crystal.
Mineral Identification
Saturday, April 29,
2017
Mineral Identification
What differences
can you see
between these
minerals that could
help identify them?
What properties
could be used to
identify minerals?
There are six main characteristics
that we will use to identify minerals:
– 1. color
– 2. crystals (the shape of)
– 3. hardness
– 4. streak
– 5. cleavage and fracture
– 6. luster
1. Color
Color - It's pretty
easy to tell the
color of a mineral
and it can give a
clue to the identity
of the mineral.
However, color
alone cannot
identify a mineral.
For example, pyrite
(fools gold) and
gold are both the
same color.
In addition, a mineral can
come in more than one
color.
For example, the mineral
corundum can occur in
several different colors
due to impurities.
Corundum is better
known as amethyst
(purple), emerald (green),
topaz (yellow), and ruby
(red).
In its pure form, corundum
is white.
2. Crystals
Crystal shape – Minerals
sometimes occur as
crystals. A crystal occurs
naturally and has straight
edges, flat sides, and
regular angles.
Each mineral forms a
specific shape of crystal
so it can be used for
identification purposes.
3. Hardness
Hardness – the
hardness of a
mineral can be
measured and
compared to other
minerals using the
Moh’s Hardness
Scale.
The scale goes from
one (the softest) to
10 (the hardest) and
ranks minerals on
their “scratchability”
Mineral
Mineral
Hardness
Hardness of
Common Items
talc
1 (softest)
Soft pencil point
(1.5)
gypsum
2
Fingernail (2.5)
calcite
3
Copper penny (3.5)
fluorite
4
Iron nail (4.5)
apatite
5
Glass (5.5)
feldspar
6
Steel file (6.5)
quartz
7
Streak plate (7)
topaz
8
Sandpaper (7.5)
corundum
9
Emery paper (9.0)
diamond
10 (hardest)
4. Streak
Streak – the color a
mineral leaves behind
when it is rubbed on
a hard surface
(usually a streak
plate)
Often the color a
mineral leaves behind
is different from the
color of the mineral.
5. Cleavage and Fracture
Cleavage and
Fracture –
Describes how a
mineral breaks
apart
The way a mineral
breaks apart can be a
clue to its identity.
If it breaks along
smooth, flat surfaces,
or planes, it is said to
have cleavage.
e.g. calcite or mica Mica can be pulled
apart into thin, flat,
sheets and Halite
forms flat edges
when broken.
If it breaks with
rough or jagged
edges, it is said
to have fracture.
E.g. obsidian
Obsidian
fractures when
broken apart
leaving rough,
jagged edges.
6. Luster
Luster – the way a mineral
reflects light
The "shininess," or luster of a
mineral depends on how light is
reflected from its surface.
The surface of a
mineral can
reflect light in
many different
ways including:
1. Metallic
Luster - the
mineral reflects
light like a
polished piece
of metal.
2. Dull Luster the mineral
scatters the
light and will not
appear shiny at
all.
Other Distinguishing Factors
Density
Magnetism
Reactivity
Senses