PHYSICAL SCIENCE 120 PHYSICAL PROPERTIES OF MINERALS

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PHYSICAL SCIENCE 120PHYSICAL PROPERTIES OF
MINERALS

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TABLE OF CONTENTS
Physical Science 120 students are required to do
pages 1 54.
Mineral Definition.Slide
3 Hardness..8 Cleavage.
...12 Fracture.....19 Streak
21 Luster....23 Color
.28 Specific Gravity....31 Taste
.48 Magnetism49 Double
Refraction53 Reaction to HCl
(acid).54 Diaphaneity..56 Crys
tals.60 Isometric...62
Hexagonal.66 Tetragonal
.70 Orthorhombic....74 Monoclinic
....79 Triclinic.82 Resources
..85
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various topics of the presentation. ()
During the presentation you can right mouse
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Mineral Identification Basics

• What is a Mineral?

There is a classic four part definition for
mineral. Minerals must be ()

• Naturally occurring ()
• Inorganic ()
• Possess a definite crystalline structure ()
• Have a definite chemical composition ()

Cubic Fluorite Crystal
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Mineral Identification Basics

• What is a Mineral?

Naturally Occurring ()

• Minerals are not synthetic - they are produced
  by the natural geological processes working on
  Earth. For example, steel, brass, bronze and
  aluminum are not considered minerals in that they
  are not found in nature. ()
• Technically speaking, synthetic gemstones are not
  considered minerals. This area of mineralogy has
  a hazy boundary in that synthetic stones are in
  every way the same as the natural stones. But
  because they are produced in laboratories, they
  do not meet the classic definition of a mineral.
  ()
• Also note that many synthetic gemstones are
  doped with a fluorescent dye to distinguish
  them from natural stone. ()

Tourmaline Crystal from Brazil
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Mineral Identification Basics

• What is a Mineral?

Inorganic ()

• Minerals are NOT produced by organic processes.
  As a result things like pearls, coral, coal and
  amber are not considered minerals.
• Also included in this
• NOT a Mineral List are teeth, bones, sea
  shells and even kidney stones. ()

Barite Rose - A flower like growth of Barite
crystals.
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Mineral Identification Basics

• What is a Mineral?

Internal Structure
Minerals are the result of atoms joining together
through electrical bonds to produce a definite
internal structure. ()
It is the nature of the atoms and the strength of
the chemical bonds that determine many of the
minerals physical and chemical properties. ()
Crystalline Pattern of Halite Red Sodium Green
Chlorine
Halite (salt) from Searles Lake, CA
()
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Mineral Identification Basics

• What is a Mineral?

Definite Chemical Composition ()

• Minerals can be expressed by a chemical
  formula. The internal order of minerals means
  that there is a definite relationship in the
  number of atoms that makes up the mineral. ()

Halite - NaCl For every atom of Sodium there is
an atom of Chlorine.
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Mineral Identification Basics

• PHYSICAL PROPERTIES HARDNESS

HARDNESS is defined as the resistance a mineral
has to being scratched - its scratchability.
Hardness tests are done by scratching one mineral
against another. The mineral that is scratched
is softer than the other. ()
Pyrite Crystals Hardness of 6.5 ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES HARDNESS

In this photo, a quartz crystal will be rubbed
across a glass plate. The result is that the
glass plate will be scratched. The quartz is
therefore harder than the glass. ()
HINT In doing a hardness test try to pick a
smooth or flat surface on the mineral to be
scratched. Try to pick a point or a sharp edge
on the mineral that you think will do the
scratching. Glass is usually a good place to
start because it is in the middle of the hardness
table, it has a flat, smooth surface and it is
easily obtained. ()
Quartz is harder than glass.
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Mineral Identification Basics

• PHYSICAL PROPERTIES HARDNESS

Care must be taken on some minerals that crumble
easily. Remember that hardness is the resistance
a mineral has to being scratched - NOT how easily
it breaks apart. The physical property related
to the ease in which a mineral breaks is
tenacity. ()
Also be sure to determine the hardness of a
mineral on a fresh surface whenever possible.
Some minerals have a tendency to oxidize or
corrode. These surface deposits usually have a
different hardness than the fresh mineral. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES HARDNESS

MOHS SCALE OF MINERAL HARDNESS
1. TALC 2. GYPSUM 3. CALCITE 4. FLUORITE 5.
APATITE ()
6. FELDSPAR 7. QUARTZ 8. TOPAZ 9.
CORUNDUM 10. DIAMOND ()
OTHER MATERIALS COMMONLY USED 2.5 -
FINGERNAIL 3 - COPPER PENNY 5.5 -
GLASS 6-6.5 - STEEL
FILE
Mohs scale is a list of minerals with increasing
hardness.()
()
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

CLEAVAGE is the property of a mineral that allows
it to break repeatedly along smooth, flat
surfaces. ()
These GALENA cleavage fragments were produced
when the crystal was hit with a hammer. Note the
consistency of the 90o angles along the edges.
()
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

Within this crystalline pattern it is easy to see
how atoms will separate to produce cleavage with
cubic (90o) angles. ()
It is similar to tearing a piece of paper that
has perforations in it. The paper has a tendency
to tear along the perforations. They are zones
of weakness. ()
In this example the lines represent breaks
between the atoms that make up the mineral.
Cleavage is guided by the atomic structure. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

These pictures show different cleavage angles and
the quality of cleavage.
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

Common salt (the mineral HALITE) has very good
cleavage in 3 directions. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

()
Even these tiny fragments have rhombohedral
cleavage. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

Blocky Cleavage 2 directions
Note that the faces in the circle are at
different levels. By adjusting the lighting, all
of the parallel faces will reflect
simultaneously. This results in a flash of light
from all the parallel faces. ()
Orthoclase feldspar has good cleavage in 2
directions. The blocky appearance of this
specimen is a hint that it has cleavage. The
clue that the specimen has cleavage is the fact
that numerous faces will reflect light at the
same time. Each face is parallel and light will
reflect of each face producing a flash of light.
()
Orthoclase Feldspar ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES CLEAVAGE

TALC has micaceous cleavage. That is to say that
it cleaves like mica (1 perfect direction) but,
in talc the crystals are so small that they
cannot easily be seen. Instead the effect is
that the talc feels soapy. The second picture
shows some of the talc that has cleaved onto the
fingers. ()
()
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Mineral Identification Basics

• PHYSICAL PROPERTIES FRACTURE

FRACTURE is defined as the way a mineral breaks
other than cleavage. ()
This is a piece of volcanic glass called
OBSIDIAN. Even though it is NOT a mineral, it is
shown here because it has excellent conchoidal
fracture. ()
If you try this yourself, use caution.
Conchoidal fracture in obsidian can produce
extremely sharp edges. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES FRACTURE

This Quartz crystal will be struck with a hammer
to show how that the external form of the crystal
does not repeat when broken. (The flat crystal
faces are not cleavage faces.) This is a good
example of conchoidal fracture. ()
Note the smooth curved surfaces.
()
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Mineral Identification Basics

• PHYSICAL PROPERTIES STREAK

STREAK is defined as the color of the mineral in
powder form. ()
Streak is normally obtained by rubbing a mineral
across a streak plate. This is a piece of
unglazed porcelain. The streak plate has a
hardness of around 7 and rough texture that
allows the minerals to be abraded to a powder.
This powder is the streak. ()
Hematite has a reddish brown streak. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES STREAK

Sphalerite is a dark mineral, however, it has a
light colored streak. Next to the reddish brown
streak of hematite is a light yellow streak.
This is the streak of the sphalerite. ()
Light colored streaks are often difficult to see
against the white streak plate. It is often
useful to rub your finger across the powder to
see the streak color. ()
Sphalerite has a light yellow streak. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES LUSTER

LUSTER is defined as the quality of reflected
light. Minerals have been grossly separated into
either METALLIC or NON-METALLIC lusters.
Following are some examples ()
Native Silver has a Metallic Luster. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES LUSTER METALLIC

The basic idea for Metallic Luster is that the
minerals look like metals. ()
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Mineral Identification Basics

• NON-METALLIC LUSTER VITREOUS

Vitreous Luster means that the mineral has a
glassy look. Normally we think of glass as
being clear, but there are many different colors
of glass and they are all very glassy looking.
Even china plates and glazed porcelain are
vitreous. Here are some examples ()
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Mineral Identification Basics

• NON METALLIC LUSTER

Miscellaneous Lusters
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Mineral Identification Basics

• PHYSICAL PROPERTIES LUSTER

The moral to this story is to look at a fresh
surface whenever possible.()
This piece of Native Copper is severely
weathered. It does not look metallic. ()
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Mineral Identification Basics

• PHYSICAL PROPERTIES COLOR

The COLOR of a mineral is usually the first thing
that a person notices when observing a mineral.
However, it is normally NOT the best physical
property to begin the mineral identification
process. ()
Following are some examples of color variation
within mineral species followed by minerals that
have a distinctive color ()
Various colors of CALCITE. ()