Minerals
Gypsum Crystals (actual size)
Elements and Minerals
• 87 naturally occurring elements
• 12 are found in the earth’s crust in
amounts >1%
• These twelve make up 99% of the mass of
the crust.
• 70% of the crust is Oxygen and Silicon.
Recall that the inner
planets formed
predominantly from
the cosmically
abundant refractory
elements:
Iron
Silicon
Magnesium
Sulfur
and their
oxides.
Melting of the young Earth
caused iron metal and
siderophile elements to
concentrate in the core and
lighter elements and oxides
to concentrate in the rocky
mantle and crust.
Depleted
in the
crust
Rock-Forming
Minerals
Silicates
Labradorite Quartz
K-Feldspar Kaolinite
Ore Minerals
Oxides
Hematite
Sulphate
Gypsum
Limonite
Native
Graphite
Albite
Hornblende
Magnetite
Garnet
Augite
Muscovite
Olivine
Sulfides
Pyrite
Biotite
Talc
Galena
Calcite Carbonate
Halide
Halite
Mineral Families
Elements, Minerals, and Rocks
•
•
87 Naturally occurring elements.
> 4000 known minerals composed of elements.
•
•
•
•
Single element (e.g. diamond)
Simple compounds (e.g. CO2)
Complex compounds (e.g. CaCO3)
Rocks are composed of aggregates of minerals.
•
•
12 minerals compose the bulk of all rocks
Rocks are classified into one of three families
depending on how they formed.
• Igneous, Metamorphic, Sedimentary
wood
CFRP
CO2
Minerals
coal
graphite
carbon dioxide
calcite
diamond
Materials Containing Carbon
Why are some of these minerals and some not?
Mineral Properties
• Minerals have a distinct and consistent elemental
composition (e.g. CaCO3).
• Minerals have a crystalline structure (atoms form
indefinitely repeating groups).
• Minerals are solid (liquids and gases cannot be
crystalline).
• Minerals are inorganic by definition (excludes C-H
organic molecules).
• Minerals are naturally occurring by definition.
Mineral Properties
• Naturally occurring substances that violate one or two of
the above criteria are called mineraloids. Examples
include: amber, obsidian, opal, coal, mercury, and petroleum.
Opal
Amber
Coal
Mercury
Carbon as a Mineral
• Minerals made of pure carbon
–Graphite (pencil lead)
–Diamond (gemstone)
• Minerals made of carbon + other elements
– Pearl [CaCO3] (semi-precious gem)
– Azurite [Cu3(CO3)2(OH)2] (pigment, semi-precious gem)
– Siderite [FeCO3] (low grade iron ore)
Malachite
copper carbonates
Pearl
(calcium
carbonate)
Complex Carbon
Minerals
Siderite
(iron carbonate)
Azurite
Simple Carbon Minerals
Diamond
Conditions required for diamond formation
Kimberlite - rock
produced by
explosive
eruption of
mantle magma.
Kimberlite with
mantle inclusions
Diamond crystal
American
Cut
Cut Diamond
Questions for Discussion
What are some of
the physical
properties of
diamond?
Why are diamonds
useful? Why are they
so valuable?
What are the optical properties of
Diamond?
Refraction of light inside a properly cut diamond.
Physical Properties of Diamond Mineral
•
Hardest naturally occurring substance (only
another diamond can scratch a diamond - Mohs
hardness of 10).
•
•
•
Brilliance (caused by high index of refraction)
•
All of these properties are related to the crystal
structure of diamond.
Fire (caused by high dispersion)
High thermal conductivity (“ice” - diamond feels
cold to the touch)
• Carbon atoms are tightly packed.
• Short atomic bonds are very strong.
• Diamond is very dense - conducts heat and bends light.
Simple Carbon Minerals
Graphite
Questions for Discussion
What are some of
the physical
properties of
graphite?
What are some of
the practical uses of
graphite?
Physical Properties of Graphite Mineral
•
One of the softest naturally occurring substances (Mohs
hardness of 1).
•
•
•
Opaque
•
All of these properties are related to the crystal
structure of graphite.
Slightly metallic luster (looks ‘steely’)
Slippery or greasy to the touch - used as a dry
lubricant
• Carbon atoms are arranged in tightly connected sheets.
• Electrostatic bonds between sheets are very weak.
• Sheets break away from one-another very easily.
Diamond
Graphite
Crystal Structure
Questions for Discussion
Is water a mineral?
Why or why not?
LR
Is glass a mineral?
Why or why not?
LF
Is sugar a mineral?
Why or why not?
RR
Is plastic a mineral?
Why or why not?
RF