I. What is a Mineral?

Naturally-formed, inorganic, solid
substance with a crystalline structure
and definite chemical composition.
Pyromorphite
What do all minerals have in
common?
All:
1.
2.
3.
4.
5.
Are formed by natural processes.
Are NOT alive and NEVER were alive
(inorganic)
Have a definite volume and shape (solid)
Are elements or compounds with a unique
chemical makeup
Are made up of particles that are arranged in
a pattern that is repeated over and over called
a CRYSTAL. (crystalline structure)
II. How do minerals form?

1) Cooling of magma which is hot, liquid
rock and minerals inside the earth
(comes from the mantle)



Fast Cooling = No Crystals
Medium Cooling = small crystals
Slow Cooling = large crystals
How do minerals form?

2) Elements dissolved in liquids (usually
water)


The mineral filled water is superheated and
shot through cracks in the surrounding
rocks and eventually the minerals
crystallize…OR
The mineral filled water drips through the
ground and as it does, the water evaporates
leaving behind crystallized mineral deposits
III. Groups of Minerals

Minerals are grouped by the elements
they are made of.
Beryl (Emerald)
Calcite
Amethyst
Mineral Group
Characteristics
Contain
Silicates
MICA
oxygen & silica
The most
abundant group
of minerals
Known as the
Rock Forming
minerals
Examples
Quartz, mica
Quartz
Mineral Group
Characteristics
Make
Non-Silicates
Ruby
up only
5% of the
Earth’s crust
Include some
of the most
important
minerals
Examples
iron, rubies
Iron
Mineral Group
Carbonates
Characteristics
Contain
Carbon, oxygen,
and a positive
ion, such as
calcium
Examples
Calcite (CaCO3)
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),
Silver (Ag)
IV. Crystal structure



Crystal structure depends on sizes of, and
charges on ions
Most common mineral group is the
silicates
All silicate minerals contain silicon and
oxygen
Silicate mineral structures
Basic building block: silica tetrahedron
Silica tetrahedron is a silicon ion bonded to 4 oxygen ions
Net charge on tetrahedron: -4
Because entire tetrahedron is negatively charged, it is
attracted to cations (positive charge)
Single chain silicates
Adjacent tetrahedra form a chain by sharing 2 of their oxygens with
neighboring tetrahedra
e.g. pyroxenes
Double chain silicates
Two chains can link up by sharing oxygens
e.g. amphiboles
Sheet silicates
Sheets are formed when each tetrahedron shares 3 of its oxygens with its
neighbors
e.g. micas, biotite and muscovite
Silicate Structures
Other Crystal Structures
1.What element are diamonds made from?
2. What effect does changing the crystal
structure have?
Diamond
Graphite
V. Physical Properties of Minerals
(can be used to identify the mineral)
Color
 Can be misleading
 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
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’t help identify quartz
http://www.childrensmuseum.org/geomysteries/cube/b3.html
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)

Find out more…

“Electronic” Hardness Test
http://www.childrensmuseum.org/geomy
steries/cube/b2.html
Physical Properties of Minerals
(can be used to identify the mineral)
Cleavage & Fracture



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
Cleavage or Fracture?
1.
4.
2.
3.
Physical Properties of Minerals
(can be used to identify the mineral)
Other Properties



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Specific gravity (*excellent clue to
mineral’s identity) http://www.childrensmuseum.org/geomysteries/cube/b4.html
Attraction to magnets
Bending of light
Reaction with hydrochloric acid
Smell & taste