Minerals and
Rocks
www.middleschoolscience.com 2009
http://www.gc.maricopa.edu/earthsci/imagearchive/index.htm
 Solid
 Cannot be a liquid or a gas
 Naturally Occurring
 Found in nature, not man-made
 Inorganic
 Is not alive and never was, non-living
 Fixed composition
 Has a chemical formula, most are formed from
compounds of two or more elements, some minerals
consist of one element ex. Au
 Crystal Form
 A definite structure in which atoms are arranged
• Is it non-living material?
• Is it a solid?
• Is it formed in nature?
• Does it have a crystalline structure?
Gold
Fossil
Topaz
Bones
Granite
Quartz
Pearls
Talc
Icebergs
Diamond
Coal
Rock Salt
 Minerals
 Non-Minerals
a) Gold
a) Wood - once living
b) Topaz
b) Fossils – once living
c) Quartz
c) Bone - living material
d) Talc
d) Granite - intrusive igneous rock
e) Iceberg*
e) Pearls – made by oysters
f) Diamonds
f) Coal - Sedimentary rock
g) Rock Salt – Sedimentary rock
According to IMA – ice is listed as a mineral
A mineral is a naturally formed,
inorganic solid that has a
definite crystalline structure.
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
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 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.
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
Stibnite
Pyrite
LUSTER METALLIC
Galena
Marcasite
Mineral Identification Basics
 NON-METALLIC LUSTER VITREOUS
Olivine - Peridot
Quartz
Wulfenite
Spinel
Mineral Identification Basics
 NON METALLIC LUSTER
Miscellaneous Lusters
Asbestos - Silky
Apophyllite - Pearly
Graphite has a greasy or submetallic luster
and
easily marks
paper.
Sphalerite
- Resinous
Limonite - Dull or Earthy
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
Mineral Identification Basics
 INDICATIVE COLOR
Azurite
Turquoise
Rhodochrosite
Sulfur
Malachite
Mineral Identification Basics
 PHYSICAL PROPERTIES SPECIFIC GRAVITY
The SPECIFIC GRAVITY of a
mineral is a measure of the
mineral’s density. It is related
to the types of elements that
make up the mineral and how
they are packed into the
mineral’s atomic structure.
Gold in Quartz
Gold has a Specific Gravity of 19.2.
It is 19.2 times the weight of an
equal volume of water.
Water has a Specific Gravity of 1.
Mineral Identification Basics
 PHYSICAL PROPERTIES SPECIFIC GRAVITY
The SPECIFIC GRAVITY of a mineral is determined by
weighing the specimen in air and then weighing it in water.
It is the ratio of an object’s density to the density of water.
Specific Gravity =
Weight in air
(Weight in air) - (Weight in water )
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
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 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 #
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Record Data
MINERAL #
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Record Data