Where do Minerals Come From? pg 16 Minerals from Magma Magma comes from the mantle and cools. When...
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Where do Minerals Come From? pg 16 Minerals from Magma Magma comes from the mantle and cools. When it cools, it forms into minerals If it cools slowly,
Where do Minerals Come From? pg 16 Minerals from Magma Magma
comes from the mantle and cools. When it cools, it forms into
minerals If it cools slowly, it forms large crystals. If it cools
fast, it forms small crystals.
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Minerals from Solutions Minerals can dissolve into a solution.
When enough minerals are in the solution, they stick together and
precipitate. They form a solid while still in the solution.
Minerals can also crystalize when the solution evaporates (called
evaporates)
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WELCOME TO THE GLENDALE COMMUNITY COLLEGE presented by: Susan
Celestian - Curator of the Arizona Mining and Mineral Museum Stan
Celestian - Photographer MINERAL IDENTIFICATION PROGRAM copyright
2002
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Mineral Definition.Slide 4 Hardness..9 Cleavage....13
Fracture.....20 Streak22 Luster....24 Color.29 Specific
Gravity...32 Taste.41 Magnetism42 Diaphaneity..46 Double
Refraction50 Reaction to HCl (acid)..51 Crystals.52 Isometric...54
Hexagonal.58 Tetragonal.62 Orthorhombic...66 Monoclinic...71
Triclinic74 Resources.77 TABLE OF CONTENTS
Slide 8
Introduction to Mineral Identification Basics Welcome to the
fascinating world of Minerals. The purpose of this CD is to present
you with some of the basic techniques used to identify minerals.
This Power Point Presentation can also be viewed in the edit mode.
Here you can view the many notes associated with the slides.
Slide 9
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
Slide 10
Mineral Identification Basics What is a Mineral? 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 Naturally
Occurring
Slide 11
Mineral Identification Basics What is a Mineral? 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. Inorganic
Slide 12
Mineral Identification Basics What is a Mineral? Minerals are
the result of atoms joining together through electrical bonds to
produce a definite internal structure. Crystalline Pattern of
Halite Red = Sodium Green = Chlorine Internal Structure Halite
(salt) from Searles Lake, CA It is the nature of the atoms and the
strength of the chemical bonds that determine many of the minerals
physical and chemical properties.
Slide 13
Mineral Identification Basics What is a Mineral? 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. Definite Chemical Composition
Slide 14
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
Slide 15
Mineral Identification Basics PHYSICAL PROPERTIES HARDNESS In
this photo, a quartz crystal has been rubbed across a glass plate.
The result is that the glass plate was scratched. The quartz is
therefore harder than the glass. Quartz is harder than 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.
Slide 16
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.
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 90 o angles along the edges. These are
FLUORITE cleavage fragments.
Slide 19
Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
Within this crystalline pattern it is easy to see how atoms will
separate to produce cleavage with cubic (90 o ) angles.
Slide 20
Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
These pictures show different cleavage angles and the quality of
cleavage. Fluorite has cleavage in four directions A thin sheet of
Muscovite seen on edge. Mica has perfect cleavage in ONE
direction.
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Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
Common salt (the mineral HALITE) has very good cleavage in 3
directions. These 3 directions of cleavage are mutually
perpendicular resulting in cubic cleavage.
Slide 22
Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
Rhombohedral Cleavage - 3 directions CALCITE Even these tiny
fragments have rhombohedral cleavage.
Slide 23
Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
Blocky Cleavage 2 directions Orthoclase Feldspar 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. 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.
Slide 24
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.
Slide 25
Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
FLUORITE cleavage octahedron
Slide 26
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 has been struck with a hammer to show how the
external form of the crystal does not repeat when broken. This is a
good example of conchoidal fracture. Note the smooth curved
surfaces.
Slide 28
Mineral Identification Basics PHYSICAL PROPERTIES STREAK STREAK
is defined as the color of the mineral in powder form. Hematite on
Streak Plate 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.
Slide 29
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. Sphalerite has
a light yellow streak. 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.
Slide 30
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
Mineral Identification Basics NON METALLIC NON METALLIC LUSTER
Miscellaneous Lusters Asbestos - SilkyApophyllite - Pearly Limonite
- Dull or Earthy Sphalerite - Resinous Graphite has a greasy or
submetallic luster and easily marks paper.
Slide 34
Mineral Identification Basics PHYSICAL PROPERTIES LUSTER This
piece of Native Copper is severely weathered. It does not look
metallic. This is the same piece but the left side has been buffed
with a steel brush. Note the bright metallic luster. The moral to
this story is to look at a fresh surface whenever possible.
Slide 35
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.
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Clear - Without Impurities Mineral Identification Basics
PHYSICAL PROPERTIES COLOR Various colors of Quartz. Hematite
Inclusions Chlorite inclusions Amethyst Ionic Iron
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Mineral Identification Basics INDICATIVE COLOR Turquoise Sulfur
Malachite Rhodochrosite Azurite End Day 1
Slide 38
Mineral Identification Basics PHYSICAL PROPERTIES TASTE IT IS
NOT RECOMMENDED THAT A TASTE TEST BE PERFORMED ON MINERALS AS A
STANDARD PROCESS. SOME MINERALS ARE TOXIC. However, the mineral
HALITE is common salt and has a unique taste. Halite cubes from
Trona, CA include picture of salt and salt shaker
Slide 39
Mineral Identification Basics PHYSICAL PROPERTIES MAGNETISM
MAGNETISM is the ability of a mineral to be attracted by a magnet.
This most commonly is associated with minerals rich in iron,
usually magnetite. This is a piece of MAGNETITE with a magnet
adhering to it. Magnetite is strongly magnetic in that a magnet
will easily be attracted to it.
Slide 40
Mineral Identification Basics PHYSICAL PROPERTIES MAGNETISM
More sensitivity is achieved if instead of a large sample, small
pieces are used. In this way, even weakly magnetic minerals will be
attracted to the magnet.
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Mineral Identification Basics PHYSICAL PROPERTIES MAGNETISM
This is a sample of black sand from Lynx Creek, Arizona. Its dark
color is due to its high concentration of magnetite. See what
happens when a magnet is place beneath the bottom right portion of
the paper. This technique is used to separate out much of the
unwanted material in the search for gold in placer deposits.
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Mineral Identification Basics PHYSICAL PROPERTIES MAGNETISM
LODESTONE is a variety of Magnetite that is naturally a
magnet.
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Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
The manner in which minerals transmit light is called DIAPHANEITY
and is expressed by these terms: TRANSPARENT: A mineral is
considered to be transparent if the outline of an object viewed
through it is distinct. TRANSLUCENT: A mineral is considered to be
translucent if it transmits light but no objects can be seen
through it. OPAQUE: A mineral is considered to be opaque if, even
on its thinnest edges, no light is transmitted. Quartz with
Spessartine Garnets
Slide 44
Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
TRANSPARENT: A mineral is considered to be transparent if the
outline of an object viewed through it is distinct. Topaz from
Topaz Mountain, Utah
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Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
Sylvite from Salton Sea, California TRANSLUCENT: A mineral is
considered to be translucent if it transmits light but no objects
can be seen through it. Backlit Apophyllite Crystals
Slide 46
Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
Schorl - The black variety of Tourmaline OPAQUE: A mineral is
considered to be opaque if, even on its thinnest edges, no light is
transmitted.
Slide 47
Mineral Identification Basics DOUBLE REFRACTION DOUBLE
REFRACTION : Is a property shared by many minerals ( but not those
in the isometric crystal system). It is best displayed in the
mineral CALCITE. This image clearly shows the double image below
the calcite
Slide 48
Mineral Identification Basics CHEMICAL PROPERTIES REACTION TO
HYDROCHLORIC ACID Some minerals, notably the carbonates, react to
cold dilute HCl. In this illustration a piece of CALCITE is shown
to react (fizz) after HCl is applied. Calcite Reacts to HCl
Slide 49
Density How much mass is in a given volume. D = m/v
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Mineral Identification Basics PHYSICAL PROPERTIES CRYSTALS A
CRYSTAL is the outward form of the internal structure of the
mineral. The 6 basic crystal systems are: ISOMETRIC HEXAGONAL
TETRAGONAL ORTHORHOMBIC MONOCLINIC TRICLINIC Drusy Quartz on
Barite
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Mineral Identification RESOURCES
http://www.gc.maricopa.edu/earthsci/imagearchive/index.htm For lots
of useful images of minerals and more facts about minerals, check
out this web site:
Slide 52
This copyrighted Power Point CD was produced strictly for
educational purposes. Any attempt at using the images within this
program for monetary gain is illegal. The authors have given
permission to use the program or parts of it, provided credit is
given to the Arizona Mining and Mineral Museum, its Curator - Susan
Celestian and the photographer - Stan Celestian. THE END