What is a mineral?
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Naturally occurring
Solid substance
Orderly crystalline structure
Definite chemical composition
Generally INORGANIC
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Some animals secrete inorganic compounds
(Calcium carbonate found in shells and coral
reefs)
Characteristics of Minerals
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More than 4000 minerals
identified, but only 20 are
commonly found
Those 20 are known as rockforming minerals, form the
rocks of Earth’s crust
Of the 20 most common, half
of them make up 90% of the
mass of Earth’s crust
Groups of Minerals
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Minerals are classified by the elements
they are made of.
Beryl (Emerald)
Calcite
Amethyst
Mineral Group
Characteristics
Contain
Silicates
oxygen & silica
The most
abundant group
of minerals
(95%)
MICA
Examples
Quartz, mica
Quartz
Mineral Group
Characteristics
Make
Non-Silicates
Silver
up only
5% of the
Earth’s crust
Include some
of the most
important
minerals
Examples
iron, copper,
gold, silver,
diamonds,
rubies
Copper
Diamond
Gold
Ruby
Iron
Mineral Group
Carbonates
Characteristics
Carbon
Examples
&
Calcite (CaCO3)
oxygen and a
positive ion,
such as calcium
Calcite with Duftite inclusions
Mineral Group
Oxides
Characteristics
Metallic
ion
and oxygen
Examples
Hematite
(Fe2)O3
Mineral Group
Sulfides
Characteristics
Sulfur
and a
metallic ion
Examples
Galena (PbS)
Mineral Group
Sulfates
Barite on Calcite
BaSo4 / CaCO3
Characteristics
Metallic
Sulfur &
oxygen
ion,
Barite
BaSo4
Examples
Barite (BaSO4)
Mineral Group
Native
Elements
Characteristics
Single
elements
Examples
Gold (Au),
Diamond (C),
Silver (Ag)
Chemical Formulas to Know
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Gold - Au
Silver - Ag
Copper - Cu
Sulfur - S
Diamond - C
Graphite - C
Platinum - Pt
Quartz - SiO2
Olivine - (Mg,
Fe)2SiO4
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Hematite - Fe2O3
Magnetite - Fe3O4
Corundum - Al2O3
Galena - PbS
Sphalerite - ZnS
Pyrite - FeS2
Halite - NaCl
Fluorite - CaF2
Calcite - CaCO3
Crystal Structure
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All minerals have a
crystalline structure
A crystal is a solid
whose atoms, ions, or
molecules are
arranged in a regular,
repeating pattern
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Each type of mineral
crystal is defined by a
specific geometric
arrangement of atoms
Physical Properties of Minerals
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Color
Luster
Streak
Hardness
Cleavage
Fracture
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Crystal System
Density
Special Properties
Physical Properties of Minerals
(can be used to identify the mineral)
Color
 Can be misleading
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For example, Quartz comes in a variety of
colors
Can vary with the type of impurities
Physical Properties of Minerals
(can be used to identify the mineral)
Luster
 Surface reflection
 metallic = shiny like
metal
 non-metallic = dull,
non-shiny surface
Pyrite has a metallic luster
Calcite has a non-metallic luster
Non-metallic Luster
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Non-Metallic lusters include:
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Vitreous (glassy)
Pearly (pearl-like)
Silky (fiber-like)
Earthy (dull)
Non-metallic luster Continued.
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Non-metallic lusters include:
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Waxy (greasy appearance)
Adamantine (diamond-like)
Resinous (plastic-looking)
Physical Properties of Minerals
(can be used to identify the mineral)
Streak
 The color of the powdered
form of the mineral
 The color of the streak can be
different than the mineral
 Minerals must be softer than
the streak plate
Streak…can help identify quartz
Can oil and natural gas be
classified as minerals? Why or
why not?
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Answer: Oil and natural gas cannot be
classified as minerals, because they are
not solids, do not form crystals, and do
not have a definite chemical make-up
Physical Properties of Minerals
(can be used to identify the mineral)
Cleavage & Fracture
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The way the mineral breaks
Cleavage—minerals break
along smooth, flat surfaces
and every fragment has the
same general shape
Fracture—minerals that break
at random with rough or
jagged edges
Types of Cleavage
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Basal - 1 plane
Prismatic - 2 planes
Cubic - 3 planes @
90
Rhombohedral - 3
planes not @ 90
Octahedral - 4
planes
Dodecahedral - 6
planes
Types of Fracture
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Conchoidal – curved
Irregular – uneven
Fibrous – splintery
Hackly – jagged-edged
Physical Properties of Minerals
(can be used to identify the mineral)
Hardness
 How easily a mineral scratches
materials
 Mohs Hardness Scale
Scale from 1 (softest) to 10 (hardest)
 Test by seeing if the mineral can scratch
different objects (like human fingernail, copper,
penny, glass, steel file)
 2.5, 3.5, 5.5, 6.5
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Crystal System
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Crystal form is the visible expression of a
mineral’s internal arrangement of atoms
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Every mineral has a crystal form
Density
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Special Properties
Magnetism Attraction to magnets
Smell & taste
Fluorescence  glows under UV light
Phosphorescence  glows after UV light
is off (stores light energy longer)
Special Properties
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Effervescence  fizzing (HCl on
calcite)
Chatoyancy  silky band when light
shined on mineral
Asterism  six-sided star appears when
light
Special Properties
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Double refraction – light
is bent, causing image
to be doubled
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Ex. Calcite
Radioactivity
Geiger counter
Describe what would happen if
you rubbed a mineral with a
Mohs hardness value of 7
against a mineral with a value of
5.
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The one with a hardness of 5 would be
scratched, because the mineral with a
hardness of 7 is harder.