Transcript Minerals - SharpSchool

Minerals
Uses of …
What are
they?
Composition
Minerals
Classification
Identification
Crystal Systems
Formation of ….
What is a Mineral?
There are five criteria that a
substance must meet in order to be
considered a mineral. To be a
mineral a substance must:
1.
2.
3.
4.
5.
Be naturally occurring
Be inorganic
Be solid at room temperature
Possess a definite chemical composition
Possess a well defined crystal structure
What is a Mineral?

Minerals are naturally occurring. Minerals
are never man-made. If a substance that
is normally found in nature can be
manufactured. The manufactured material
is not considered a mineral.
Natural Diamond:
Mineral
Synthetic Diamond:
Non-Mineral
What is a Mineral?

Minerals are inorganic substances. This
means that they did not form as a result
of a biological process.
Coal: Not a Mineral
Fossilized Plant Remains
Amber: Not a Mineral
Fossilized Plant Resins
What is a Mineral?



Minerals are always solid at room temperature. The
majority of metals and non-metals of the periodic table are
minerals. There are exceptions:
The gases: H2, N2, O2, F2, Cl2, and the Noble Gases
The metal Mercury (Hg) and the non-metal Bromine (Br2)
Hg
Br2
What is a Mineral?
Minerals have definite chemical
compositions.
 Minerals are pure substances meaning
they are either compounds, or elements.
 Minerals are never mixtures

Native Copper
What is a Mineral?

Minerals have well defined crystal
structures.
Classification of Minerals
Minerals are classified according to
the following criteria:
 Chemical
Composition (eight classes)
 Crystal System (six systems)
 Method of Formation (three methods)
Chemical Composition
•Native Elements
•Silicates
•Carbonates
•Halides
•Oxides
•Hydroxides
•Sulfides
•Sulfates
Chemical Composition: Native Elements


Elements that can be found in a pure state
Common native elements include gold, silver,
and copper
Gold (Au)
Copper (Cu)
Chemical Composition: Silicates


Silica Tetrahedron

Single Chain
Double Chain
Sheet / Network Solids

The largest chemical
class of minerals.
Silicates are so
prevalent because the
silicate structure
comes in many forms.
These forms include:
individual tetrahedra,
single chains, double
chains, sheets, and
network solids
Common minerals
include: Olivine,
Orthoclase and
plagioclase Feldspars,
and Quartz
Chemical Composition: Carbonates



Carbonates include all minerals that include the
CO3-2 anion.
Common carbonates include Calcite (CaCO3) and
Dolomite (MgCO3)
Calcite is the mineral that comprises limestone
Chemical Composition: Halides
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
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Halides are minerals that contain anions from the halogen
(Gr. “Salt Forming”) family of the periodic table.
Halides will have F-, Cl-, Br-, I-, anions as part of their
chemical composition
Among the most common halides are halite (NaCl) and
Fluorite (CaF2)
Chemical Composition: Oxides and
Hydroxides
Oxides include all minerals that contain
the O-2 anion.
 Hydroxides contain the OH anion
 Common Oxides include Hematite and
Magnetite (both are iron oxides)

Chemical Composition: Sulfides
Sulfides include all minerals that contain
the S-2 anion
 Common Sulfides include Galena (PbS)
and Pyrite (FeS)

Chemical Composition: Sulfates
Sulfates include all minerals that include
the SO4-2 polyatomic anion.
 Common sulfates include Gypsum (CaSO4)
and Epsomite (MgSO4)

Crystal Systems
Cubic
Tetragonal
Orthorhombic
Hexagonal
Monoclinic
Triclinic
Crystal System: Cubic or Isometric
Crystal System: Tetragonal
Crystal System: Orthorhombic
Crystal System: Hexagonal
Crystal System: Monoclinic
Crystal System: Triclinic
Methods of Formation
Igneous
Metamorphic
Chemical
Method of Formation: Igneous Minerals
Igneous minerals are those minerals which
form from the cooling and solidification of
magmas (inside the Earth) and lavas (on
the surface of the Earth).
Quartz
Mica
Feldspar
Olivine
Method of Formation: Metamorphic Minerals
Metamorphic minerals are those that form
from pre-existing minerals that have been
exposed to high temperature and or
pressure.
Staurolite
Dioptase
Grossular
Spessartite
Chemical Formation: Evaporites
•
•
•
Evaporite minerals form as the water that
minerals are dissolved in evaporates.
Evaporation increases the concentration of a
mineral until the solution is saturated.
Any further evaporation will result in the
formation of mineral crystals.
Halite – NaCl
The blue is the result of trace
elements
Chemical Formation: Precipitates
•
•
Precipitate minerals form when the concentration of ions in
solution increases to the point that insoluble salts form and
sink to the bottom of the body of water in which it forms.
Precipitates often form in lagoons and in lakes that dry out
due to rapid evaporation, or when calcium rich fresh water
pours into ocean water with a significant amount of
dissolved CO2
Calcite – CaCO3
Dolomite – CaMg(CO3)2
How are Minerals Identified?
Minerals are identified using several
physical properties. Among the
physical properties used are:
Color
Cleavage
Hardness
Fracture
Streak
Unique - Properties
Luster
Color
Color is the least useful of all identifiable
characteristics of minerals
 The same mineral may come in many
color varieties due to the presence of
trace elements. Ex. quartz
 Many different minerals may appear to be
the same color Ex. gold and pyrite

Hardness
Hardness is the
resistance that a
mineral has to
being scratched by
another mineral.
 Mohs Scale of
Hardness is used
to determine the
hardness of a
mineral sample

Streak
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Streak is the determination of the true color of
a mineral by looking at a powdered sample of
the mineral.
Minerals are powdered by rubbing them against
a piece of unglazed porcelain plate.
Powdering the mineral eliminates the influence
of trace elements
This is most useful for minerals softer than
Mohs 7
Luster
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Luster is the quality of
the light reflected
from the surface of a
mineral.
There are over thirty
categories of luster
and it takes an expert
to differentiate them
all
In this course we will
only classify minerals
as having a metallic,
non-metallic, or glassy
luster.
Cleavage
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Cleavage occurs when minerals split along flat, smooth
surfaces.
Cleavage occurs because there is a plane of weakness created
by weak molecular bonds oriented in a particular direction
There are six types of cleavage each associated with the
number of planes involved and the angle between the cleavage
planes
Fracture
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

Fracture of mineral
samples occurs when
minerals break along
uneven, or jagged
surfaces.
Fracture occurs when
there is no particular
orientation to the
weak bonds in a
mineral, or when all
bonds are of equal
strength
There are six types of
fracture
Special Properties
 Magnetism
ex. magnetite
 Taste ex. halite
 Oder ex. sulfur and pyrite
 Phosphorescence ex. calcite
 Fluorescence ex. calcite
 Specific Gravity ex. all minerals
 Reaction with Acids/Bases ex. calcite
 Birefringence ex. calcite
Uses of Minerals
The two primary uses of minerals are:
Commercially and Strategically
Valuable Ores
Gemstones
What is an Ore?
An ore is a mineral that can be mined and
refined to extract a commercially or
strategically valuable substance
 Examples of important ores are:

hematite and magnetite (iron ores)
galena (lead ore)
sphalerite (zinc ore)
bauxite (aluminum ore)
Gemstones
 To
qualify as a gemstone a mineral
must be:
Rare – increases monetary value
Durable – increases longevity
Beautiful – increases demand
Varieties of Quartz
Different Minerals with the Same Color
Mohs Scale of Hardness