Mineral properties2

Mineral ID
How to identify a mineral by its properties


Introduction
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Which mineral
properties are
most important in
identification.
Scientists have
discovered up to
6000 minerals


Mineral Properties
To meet the definition of "mineral" used by
most geologists a substance must meet five
requirements:
1.naturally occurring
2.inorganic
3.solid
4.definite chemical composition
5.ordered internal crystalline structure


Mineral Property #1
Color & Streak

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Color is the first thing someone
notices when they view a mineral.
Color is also one of the big reasons
that attract people to minerals.
Generally speaking, color is not a
good property to be used in the
identification of minerals. It is
usually the first property to
confuse a novice collector into
making an incorrect identification.
Many minerals have different colors
and some minerals' colors are
identical to other minerals' colors.


Mineral Property #1
Color & Streak
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Streak 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.
Streak is actually the color of the
powder of a mineral. It is called
streak because the proper way to
test for streak is to rub a mineral
across a tile of white unglazed
porcelain and to examine the color
of the "streak" left behind.


Mineral Property #1
Color & Streak
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Pyrite (known as "Fool's Gold") is
always brassy yellow when found in
crystals, even broken crystals, of
any size; but when powdered,
produces a black streak.
Gold's streak, by the way, is
yellow!
Hematite's streak is blood-red

Galena's streak is lead gray


Mineral Property # 2
Luster
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A mineral’s luster is
the way in which light
reflects from the
surface.
The two major types
of luster are metallic
& nonmetallic.


Mineral Property # 2
Luster
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Some other ways to describe luster are

Dull - just a non-reflective surface of any kind
Earthy - the look of dirt or dried mud
Fibrous - the look of fibers
Greasy - the look of grease
Gumdrop - the look a sucked on hard candy
Metallic - the look of metals
Pearly - the look of a pearl
Pitchy - the look of tar
Resinous - the look of resins such as dried glue or
chewing gum
Silky - the look of silk, similar to fibrous but more
compact
Submetallic - a poor metallic luster, opaque but
reflecting little light
Vitreous - the most common luster, it simply means
the look of glass
Waxy - the look of wax

Mineral Property # 3
How a mineral breaks
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When a mineral breaks it does so
either by fracturing or by
cleaving.
Cleavage is the tendency of a
mineral to break along flat
surfaces.
Crystal cleavage is a smooth break
producing what appears to be a
flat crystal face.
Fracture is the tendency of a
mineral to break into irregular
pieces.
See Link


Mineral Property # 3
How a mineral breaks
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When a mineral breaks it does so
either by fracturing or by
cleaving.
Cleavage is the tendency of a
mineral to break along flat
surfaces.
Crystal cleavage is a smooth break
producing what appears to be a
flat crystal face.
Fracture is the tendency of a
mineral to break into irregular
pieces.


Mineral Property #4
Hardness
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A mineral’s hardness is
its resistance to being
scratched.

A scale known as the
Moh’s scale is often
use


Mohs Scale of Hardness


Mohs Scale
Rating
1
2
3
4
5
6
7
8
9
10

Type mineral
Talc
Gypsum
Calcite
Fluorite
Apatite
Feldspar
Quartz
Topaz

Corundum
Diamond

What it can be
scratched by…

Baby powder
fingernail
bronze coin
iron nail
glass
penknife blade
steel knife
sandpaper


Mineral Property #5
Density
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Each mineral has a specific density.
Density is the mass of a given space or in
scientific terms the mass per unit of
volume.
For example, if you have two minerals of

the same size one might be heavier than
the other. The galena will be three times
heavier than the same size of quartz.
See weblink



Mineral Property #5
Density
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Geologists measure density by the
following:
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First they use a balance to determine the mass
of a sample.
Second, they place the mineral in water to see
how much water it displaces.
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The volume of displace water = the volume of the
sample

Third they use the following formula:
Density = Mass/Volume