Download MINERAL FORMATION

ROCK vs. MINERAL

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
ROCK
Mixture
Can be
separated by
physical means




MINERAL
Pure
substance
Has specific
formula
Cannot be
separated by
physical means
MINERAL
FORMATION
Geology classes
FROM A MELT

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
Form from lava or
magma
most common
method
Usually forms
large crystals
example: quartz,
gemstones
From a solution

Evaporation

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
Halite, gypsum
Usually soft minerals
Precipitation from
saturated solution

Calcite, barite
From Heat and Pressure


Mainly in
metamorphic
rocks
Creates very hard
minerals
garnet
 diamonds

From Hydrothermal

Hot watery solutions
Rain water
percolates and is
heated by interior of
earth
 Chrysocolla, azurite,
gold

Classification of Minerals

Nearly 4000 minerals have been
identified on Earth
 Only 8 elements that make
up over 98% of the Earth’s
crust- THE BIG 8
ABUNDANCE OF
ELEMENTS
ELEMENT
% BY WEIGHT
OXYGEN
46.6%
SILICON
27.7%
ALUMINUM
8.1%
IRON
5.0%
CALCIUM
3.6%
SODIUM
2.8%
POTASSIUM
2.6%
MAGNESIUM
2.1%
The silicate (SiO4)-4
molecule (tetrahedron)

Wants to join with positive ions
 Fe,


Mg, K, Na, Al, Ca
Or joins with other tetrahedron (covalent)
Si joins tough with O = hard minerals (mostly)
Positive ions may
substitute for each other

If same charge and same size
 Ca
and K
 Fe and Mg


Use commas in formula to indicate
substitution
olivine
Silicate structures- most common
group of minerals
Olivine


Single tetrahedron
No cleavage
Pyroxene family- single chain
augite
2-directional clevage
AMPHIBOLE FAMILY- double chain
Hornblende crystals- 2 cleavage
MICA FAMILY

Sheet silicateone directional
cleavage


MUSCOVITE
BIOTITE
Feldspar family- most common
group
Potassium feldspar (orthoclase)
Feldspar family
Plagioclase feldspar
Quartz- Si and O only!!
Impurities


Can change
color
But not
chemistry!!
NON-SILICATES

Carbonates (CO3)


Sulfates (SO4)


gypsum
Halides (halogens)


Calcite, dolomite
fluorite
Native minerals

elements
FORMULAS
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Subscripts
Parentheses
Opal
commas