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.
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)
WELCOME TO THE
GLENDALE COMMUNITY
COLLEGE
MINERAL IDENTIFICATION
PROGRAM
presented by:
Susan Celestian - Curator of the Arizona Mining
and Mineral Museum
Stan Celestian - Photographer
© copyright 2002
TABLE OF CONTENTS
Mineral Definition……………….……Slide 4
Hardness……………………………………..9
Cleavage……………………………….…...13
Fracture……………………………..…..….20
Streak………………………………………22
Luster…………………………..……….….24
Color…………………………………….…29
Specific Gravity…………………………...32
Taste……………………………………….41
Magnetism…………………………………42
Diaphaneity………………………………..46
Double Refraction…………………………50
Reaction to HCl (acid)…………………..…51
Crystals………………………………….…52
Isometric……………………………….…..54
Hexagonal……………………………….…58
Tetragonal………………………………….62
Orthorhombic…………………………..….66
Monoclinic………………………………...71
Triclinic……………………………………74
Resources………………………………….77
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.
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
Mineral Identification Basics

What is a Mineral?
Naturally Occurring
Tourmaline Crystal from Brazil
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.
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
Barite Rose - A flower like growth
of Barite crystals.
teeth, bones, sea shells and
even kidney stones.
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
Halite (salt) from Searles Lake, CA
Green = Chlorine
Mineral Identification Basics

What is a Mineral?
Definite Chemical Composition
Halite - NaCl
For every atom of Sodium there is
an atom of Chlorine.
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.
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
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.
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 HARDNESS
MOH’S SCALE OF MINERAL HARDNESS
6. FELDSPAR
1. TALC
7. QUARTZ
2. GYPSUM
8. TOPAZ
3. CALCITE
9. CORUNDUM
4. FLUORITE
10. DIAMOND
5. APATITE
OTHER MATERIALS COMMONLY USED:
2.5 - FINGERNAIL
3 - COPPER PENNY
5.5 - GLASS
6-6.5 - STEEL FILE
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.
These are FLUORITE cleavage fragments.
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.
Mineral Identification Basics

PHYSICAL PROPERTIES CLEAVAGE
These pictures show different cleavage angles and the quality of cleavage.
Fluorite has cleavage in four
directions
Mica
A thin
has
sheet
perfect
of Muscovite
cleavage inseen
ONE
on
direction.
edge.
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.
Mineral Identification Basics

PHYSICAL PROPERTIES CLEAVAGE
Rhombohedral
Cleavage - 3 directions
CALCITE
Even these tiny fragments have rhombohedral cleavage.
Mineral Identification Basics

PHYSICAL PROPERTIES CLEAVAGE
Blocky Cleavage
2 directions
Orthoclase feldspar has good
Note
that the faces in the circle are at
cleavage in 2 directions.
Orthoclase Feldspar
different levels. By adjusting the lighting,
The
appearance
of this
specimen is
all ofblocky
the parallel
faces will
reflect
asimultaneously.
hint that it has cleavage.
that
This resultsThe
in aclue
flash
of
the
cleavagefaces
is the
lightspecimen
from all has
the parallel
. 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.
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.
Mineral Identification Basics

PHYSICAL PROPERTIES CLEAVAGE
FLUORITE cleavage octahedron
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.
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.
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 on Streak Plate
Hematite has a reddish brown streak.
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.
Mineral Identification Basics

PHYSICAL PROPERTIES LUSTER
LUSTER is defined as the
quality of reflected light.
Minerals have been grossly
separated into either
METALLIC or
NONMETALLIC lusters.
Following are some examples:
Native Silver has a Metallic Luster
Mineral Identification Basics

PHYSICAL PROPERTIES LUSTER METALLIC
Stibnite
Pyrite
Galena
Marcasite
Mineral Identification Basics

NON-METALLIC LUSTER VITREOUS
Olivine - Peridot
Quartz
Wulfenite
Spinel
Mineral Identification Basics

NON METALLIC LUSTER
Miscellaneous Lusters
Asbestos
- Silky
- Pearly
Graphite
has a greasy orApophyllite
submetallic luster
and easily marks paper.
Sphalerite - Resinous
Limonite - Dull or Earthy
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.
This is the same piece but the left
side has been buffed with a steel
brush. Note the bright metallic
luster.
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.
Mineral Identification Basics

PHYSICAL PROPERTIES COLOR
Amethyst
Ionic Iron
Clear - Without Impurities
Hematite Inclusions
Various colors of Quartz.
Chlorite inclusions
End Day 1
Mineral Identification Basics

INDICATIVE COLOR
Azurite
Turquoise
Rhodochrosite
Sulfur
Malachite
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
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.
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.
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.
Mineral Identification Basics

PHYSICAL PROPERTIES MAGNETISM
LODESTONE is a variety
of Magnetite that is
naturally a magnet.
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
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
Mineral Identification Basics

PHYSICAL PROPERTIES DIAPHANEITY
TRANSLUCENT: A mineral is
considered to be translucent if it transmits
light but no objects can be seen through it.
Sylvite from Salton Sea, California
Backlit Apophyllite Crystals
Mineral Identification Basics

PHYSICAL PROPERTIES DIAPHANEITY
OPAQUE: A mineral is considered to be
opaque if, even on its thinnest edges, no
light is transmitted.
Schorl - The black variety of
Tourmaline
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
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
Density


How much mass is
in a given volume.
D = m/v
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
TETRAGONAL
Drusy Quartz on Barite
MONOCLINIC
HEXAGONAL
ORTHORHOMBIC
TRICLINIC
Mineral Identification
RESOURCES
For lots of useful images of minerals and more facts about minerals,
check out this web site:
http://www.gc.maricopa.edu/earthsci/imagearchive/index.htm
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, providedTHE
credit is given to the Arizona Mining and
Mineral Museum, its Curator - Susan Celestian and the photographer Stan Celestian.
END