Minerals
 What
are the components of a mineral?
1. Naturally occurring
2. Inorganic solid
3. Orderly crystalline structure
4. Definite chemical composition
 Ex: Quartz  SiO2 (silicon & oxygen)

ALL rocks are COMPOSED of minerals


Minerals are formed by natural, geologic
processes
Must naturally occur in nature, cannot be
man-made
• i.e. synthetic gems are not considered
minerals.
 Minerals
are a solid….
not a liquid…not a gas.
• within temperature
ranges that are normal for
Earth.
 Inorganic
crystalline solids
found in nature
• Table salt is a mineral  inorganic
• Sugar is not mineral  organic
• Exception: many marine animals
secrete inorganic compounds
 calcium carbonate minerals (coral
reefs and in shells)

Atoms are arranged in an orderly, repetitive
structure (crystal lattice)
 Ex: gemstone opal isn’t a mineral has the same elements as
quartz (mineral) but NO orderly internal structure
Pyrite
“Fools
Gold”
FeS2

Au
A mineral has a chemical composition
defined by a chemical formula
Compounds made of 2+ elements
Exceptions: gold & silver  1 element (native form)
4
major processes by which
minerals form:
1. Crystallization from magma
2. Precipitation
3. Changes in pressure and
temperature
4. Formation from hydrothermal
solutions
• Magma = molten rock
• Magma cools
elements combine to
form minerals
• Ex: quartz &
feldspar
• First to crystallize ones
rich in iron, calcium,
and magnesium
• Each mineral begins to
crystallize at a different
temperature
 All
water in Earth’s lakes, rivers, oceans
etc. contain dissolved substances
• Water evaporates  dissolved substances react
to form minerals
• Change in water temperature  dissolved
material precipitates out
• Supersaturated
• Ex: limestone caves,
Great Salt Lake, Utah
Mono Lake, CA limestone
towers (calcite) formed
underwater from calcium rich
springs  exposed as sea
level drops
 Existing
minerals
subjected to changes in
pressure and temperature
• Increase pressure
 Minerals recrystallize while still
solid
 Atoms rearranged  forms
compacted minerals
• Change in temperature
 Minerals may become unstable
 Form new minerals  stable @
new temperature
 Very
hot mixture of water &
dissolved substances
• Have temps. between 100°C and
300°C
• Solutions come in contact w/
existing minerals chemical
reactions occur  new minerals
• Solutions cool  elements
combine
• Supersaturated
 Ex: Bornite and chalcopyrite (sulfur
minerals) formed from thermal
solutions
 Common
minerals, together with the
thousands of others that form on Earth,
can be classified into groups based on
their composition.
•
•
•
•
•
•
Silicates
Carbonates
Oxides
Sulfates and sulfides
Halides
Native elements
Okenite - a silicate
Galena - a sulfide
Fluorite - a halide
 Most common group
 Silicon and oxygen combine
form a silicon-oxygen
tetrahedron
to
• Tetrahedron consists of 1 silicon
atom & 4 oxygen atoms  silicate
 Silicon-oxygen
tetrahedra can
form chains, sheets, & 3-D
networks
• Super strong bonds
• Ex: olivine-millions of single
tetrahedra
(Fe,Mg)2SiO4) iron-magnesium silicate
 Most
silicate minerals crystallize from
magma as it cools
• Can occur at or near surface of Earth (temp. and
pressure low)
 Weathering & mountain building  form silicates
• Can occur at great depths (temp. and pressure high)
 Location
during formation & chemical
composition of magma determines which
silicate minerals will form
• Olivine: 1200°C
Quartz: 700°C
 2nd
most common mineral
group
 Contain the elements:
• carbon
• oxygen
• one or more other metallic
elements
 Calcite
(CaCO3): most
common carbonate mineral
 Limestone & marble  rocks
that are composed of
carbonate minerals
 Contains:
• Oxygen
• One or more other elements (usually metals)
 Ex: Rutile
(TiO2)
• Form as magma cools beneath Earth’s surface
• Titanium oxide
 Ex: Corundum
(Al2o3)
• Existing minerals  heat & pressure
• Aluminum oxide
 Contain
the element sulfur
 Sulfates =
• Ex: Anhydrite (CaSO4)
• Ex: Gypsum (CaSO4  2H2O)
 Forms when mineral-rich water evaporates
 Sulfides
=
• Ex: Galena (PbS)
• Ex: Pyrite (FeS2)
• Forms from thermal solutions
 Contains:
• Halogen ion
• One or more other elements
 Halogens
from Group 7A in periodic
table
• Includes fluorine and chlorine
 Halite
(NaCl) i.e. table salt
 Fluorite (CaF2) used in making steel
• Forms when salt water evaporates
 Minerals
in relatively pure form
 Ex: Gold (Au), Silver (Ag), Copper (Cu),
Sulfur (S), Carbon (C)
• Native forms of carbon are diamond and
graphite
• Some form from hydrothermal solutions