What is a Mineral?

Naturally-formed solid substance with a
crystal structure
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)
Watch “Crystals” by Brainpop…
1.What element are diamonds made from?
2. What do all crystals have in common?
Mineral Groups

Minerals are grouped by the elements
they are made of.
Beryl (Emerald)
Calcite
Amethyst
Mineral Groups – Silicates

Silicates

Tetrahedron

fundamental
building block

4 oxygen ions
surrounding a
much smaller
silicon ion
Silicon-oxygen
tetrahedron
(SiO4)4-
Mineral Groups
Non-ferromagnesian
Silicates (K, Na, Ca, Al)
Ferromagnesian
Silicates (Fe, Mg)
Oxides
Carbonates
Sulfides/sulfates
Native elements
Mineral Group
Characteristics
Contain
Silicates
oxygen & silica
The most
abundant group
of minerals
MICA
Examples
Quartz, mica
Quartz
Quartz Group
light silicates (pure SiO2)
no cleavage
(conchoidal fracture)
hard, resistant to weathering
Quartz
Feldspar Group
light silicates (K, Na, Ca, Al)
Non-ferromagnesian
Silicates
(K, Na, Ca, Al)
Plagioclase
K-feldspar
2-directions
of cleavage
(at 90 degrees)
Orthoclase
Ca/Na-feldspar
Pyroxene Groups
Augite
Ferromagnesian
Silicates (Fe, Mg)
2 directions of cleavage at nearly 90°
dark silicates (Fe-Mg)
Amphibole Groups
Non-ferromagnesian
Silicates (K, Na, Ca, Al)
Ferromagnesian
Silicates (Fe, Mg)
dark silicates (Fe-Mg)
Oxides
Carbonates
Sulfides/sulfates
Native elements
2 directions of cleavage not at 90°
Hornblende
Mica Group & Clay Minerals
Non-ferromagnesian
Silicates (K, Na, Ca, Al)
Ferromagnesian
Silicates (Fe, Mg)
Oxides
Carbonates
Sulfides/sulfates
Native elements
1 direction of cleavage
light silicates (K, Al)
Shapes of Silicates
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)
How do minerals form?

1) Cooling of magma (hot, liquid rock and
minerals inside the earth (from the
mantle))



Fast Cooling = No Crystals (mineraloids)
Medium Cooling = small crystals
Slow Cooling = large crystals
How do minerals form?

2) Elements dissolved in liquids (usually
water)
Physical Properties of Minerals
(can be used to identify the mineral)







Color
Luster
Habit (Shape)
Cleavage & Fracture
Streak
Hardness
Other
Color
-
-
Most obvious, but
often misleading
Different colors may
result from impurities;
ie., Quartz
Luster



Surface reflection
metallic = shiny like
metal
non-metallic = dull,
non-shiny surface
Metallic - pyrite
Non-metallic - calcite
Mineral Habit (Shape)
Shape a mineral
takes if grown
unimpeded
Diamond
Amethyst
Fluorite
http://www.minerals.net/MineralImageGallery.aspx
Babingtonite
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.
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
http://www.childrensmuseum.org/geomysteries/cube/b3.html
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
Other Properties

Specific gravity (*excellent clue to
mineral’s identity)

Attraction to magnets

Bending of light

Reaction with hydrochloric acid

Smell & taste
Watch Brainpop—“Mineral Identification”
1. If a mineral can scratch your fingernail,
the mineral is _______________ than
your fingernail.
2. What is luster?
Watch Classifying Minerals Clip