Download Systematic Mineralogy

Systematic Mineralogy
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Description of how minerals are divided
into groups
Groups based on anions
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Single anion (Cl-)
Anion group (SiO44-)
Further divided based on structures
Divisions
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Class (anion division)
Family (structural division – silicates
mostly)
Group (structural division)
Series (solid solution)
Species (individual minerals)
Varieties (substituted elements)
Example
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Ca-grunerite:
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A Ca-rich variety
Of a mineral species
In the cummingtonite-grunerite series
Of the amphibole group
Of the inosilicate family
Of the silicate class
Mineral class
Native elements
Oxides
Hydroxides
Halides
Sulfides
Sulfates
Carbonates
Phosphates
Silicates
Anion or anion gp
N/A
O2OHCl-, Br-, FS2SO42CO32PO43SiO44-
Silicates
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The most common group of minerals
forming Earth’s crust
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25% of all minerals (~1000)
40% of rock forming minerals
90% of earth’s crust – i.e., those minerals you
are likely to find
Silicate Structure
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Basic building block: silica tetrahedron
Si4+ with four O2- surrounding it
Net charge is 4Mesodesmic, polymerization
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Tetrahedron can share oxygen atoms
Silica Tetrahedron
Fig. 11-1
Six groups of silicate minerals
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Orthosilicates = Nesosilicates
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Disilicates = Sorosilicates
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Single tetrahedron
Two tetrahedrons share single oxygen
Ring silicates = Cyclosilicates
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4, 5, or 6 tetrahedron share two oxygen
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Chain silicates = Inosilicates
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Sheet silicates = Phyllosilicates
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2 or 3 oxygen shared, arranged in single or
double chain
3 oxygen shared in sheets
Framework silicates = Tectosilicates
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All 4 oxygen are shared
Ortho(Neso)
Di(Soro)
Ring
(Cyclo)
Sheet
(Phyllo)
Chain –
double
and
single
(Ino)
Framework
(Tecto)
Fig. 11-2
Z/O ratios
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Z = Si tetrahedral sites
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Can be other cations, most commonly Al
Z/O ratio depends on type of silicate
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Ortho = 1/4
Di = 2/7
Ring = 1/3
Chain, single = 1/3; double = 4/11
Sheet = 2/5
Framework = 1/2
Other ions
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Quartz (and polymorphs) only minerals
with only Si and O
All other silicates are charge balanced by
other cations
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“glue” that holds together silica tetrahedron
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Degree of polymerization depends on
availability of Si
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Quartz and feldspars (framework): Si-rich
environments
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Si/O = ½
Olivine (orthosilicate): Si-poor environment
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Si/O = ¼
Mafic vs Felsic
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Mafic – rich in Magnesium and Iron
(Ferrum), Si-poor
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E.g. biotite, amphiboles, pyroxenes, and
olivine
Commonly dark colored
Felsic – rich in Si and Al
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E.g. Feldspars, Quartz (SiO2), muscovite,
feldspathoids
Commonly light colored