Download Introduction to Mineralogy

Introduction to Mineralogy
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Mineralogy is a mixture of:
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New concepts – much of it from chemistry and
physics with a geologic point of view
Fairly complex ideas (but not insurmountable)
New vocabulary – many terms
Large amounts of memorization
This mixture can make mineralogy seem a bit
complicated and esoteric
So why mineralogy?
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Minerals are chemical compounds that
form from natural earth processes
Minerals are basic building blocks of rocks
Rocks provide record of earth history and
are formed by earth processes
Geologists
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Study earth history
Study earth processes
Mineralogy is the key.
Objectives
Three parts to class (originally three
classes):
Learn chemical properties of minerals
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Crystallography – spatial arrangement of
atoms
Crystal chemistry – what atoms make up
minerals and why
Analytical methods:
2.
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3.
Physical properties (this week’s lab) – visual
observations
Polarizing microscope
X-ray diffraction
Identify, classify and organize minerals
Definition of Mineral
A naturally occurring, homogeneous solid,
with a defined (but generally not fixed)
chemical composition and an ordered
atomic arrangement
1. Naturally occurring
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Why not synthetic (man-made)?
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E.g. diamonds
Corian countertops (quartz)
Table salt (halite)
Others?
San Francisco Bay
Salar de Uyuni,
Bolivian Altiplano
2. Homogeneous solid
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Minerals can not be PHYSICALLY broken
into new compounds
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How about chemically “broken”?
What would they break into?
Why solid?
Physical Reaction: Big Feldspar → Little Feldspar
Chemical reaction: Albite → Na+ + Al3+ + SiO44-
3. Defined, but not fixed,
composition
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The compositions of minerals are strictly
defined (stoichiometry), but can vary
between compositions
For example:
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Calcite is CaCO3 but will also contain much
Mg, Sr, Fe, Mn etc.
Olivine - (Fe,Mg)2SiO4 - is a group of two
main minerals:
Fayalite (Fe2SiO4)
 Forsterite (Mg2SiO4)
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4. Ordered atomic arrangement
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Crystallography – how atoms are arranged
in space.
For example:
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Aragonite (CaCO3) and calcite (CaCO3) are
different minerals but have identical
compositions
This is why minerals are referred to by name
rather than formula
Mineral names include both composition
(chemistry) and crystallography