Systematic Mineralogy Description of how minerals are divided into groups Description of how minerals are divided into groups Groups based on anions Groups based on anions Single anion (Cl - ) Single anion (Cl - ) Anion group (SiO 4 4- ) Anion group (SiO 4 4- ) Further divided based on structures Further divided based on structures

Divisions Class (anion division) Class (anion division) Family (structural division – silicates mostly) Family (structural division – silicates mostly) Group (structural division) Group (structural division) Series (solid solution) Series (solid solution) Species (individual minerals) Species (individual minerals) Varieties (substituted elements) Varieties (substituted elements)

Example Ca-grunerite: Ca-grunerite: A Ca-rich variety A Ca-rich variety Of a mineral species Of a mineral species In the cummingtonite-grunerite series In the cummingtonite-grunerite series Of the amphibole group Of the amphibole group Of the inosilicate family Of the inosilicate family Of the silicate class Of the silicate class

Mineral class Anion or anion gp Native elements N/A Oxides O 2- Hydroxides OH - Halides Cl -, Br -, F - Sulfides S 2- Sulfates SO 4 2- Carbonates CO 3 2- Phosphates PO 4 3- Silicates SiO 4 4-

Silicates The most common group of minerals forming Earth’s crust The most common group of minerals forming Earth’s crust 25% of all minerals (~1000) 25% of all minerals (~1000) 40% of rock forming minerals 40% of rock forming minerals 90% of earth’s crust – i.e., those minerals you are likely to find 90% of earth’s crust – i.e., those minerals you are likely to find

Silicate Structure Basic building block: silica tetrahedron Basic building block: silica tetrahedron Si 4+ with four O 2- surrounding it Si 4+ with four O 2- surrounding it Net charge is 4- Net charge is 4- Mesodesmic, polymerization Mesodesmic, polymerization Tetrahedron can share oxygen atoms Tetrahedron can share oxygen atoms

Fig Silica Tetrahedron

Six groups of silicate minerals Orthosilicates = Nesosilicates Orthosilicates = Nesosilicates Single tetrahedron Single tetrahedron Disilicates = Sorosilicates Disilicates = Sorosilicates Two tetrahedrons share single oxygen Two tetrahedrons share single oxygen Ring silicates = Cyclosilicates Ring silicates = Cyclosilicates 4, 5, or 6 tetrahedron share two oxygen 4, 5, or 6 tetrahedron share two oxygen

Chain silicates = Inosilicates Chain silicates = Inosilicates 2 or 3 oxygen shared, arranged in single or double chain 2 or 3 oxygen shared, arranged in single or double chain Sheet silicates = Phyllosilicates Sheet silicates = Phyllosilicates 3 oxygen shared in sheets 3 oxygen shared in sheets Framework silicates = Tectosilicates Framework silicates = Tectosilicates All 4 oxygen are shared All 4 oxygen are shared

Fig Ortho-(Neso) Di-(Soro) Ring(Cyclo) Chain – double and single (Ino) Framework (Tecto) Sheet(Phyllo)

Z/O ratios Z = Si tetrahedral sites Z = Si tetrahedral sites Can be other cations, most commonly Al Can be other cations, most commonly Al Z/O ratio depends on type of silicate Z/O ratio depends on type of silicate Ortho = 1/4 Ortho = 1/4 Di = 2/7 Di = 2/7 Ring = 1/3 Ring = 1/3 Chain, single = 1/3; double = 4/11 Chain, single = 1/3; double = 4/11 Sheet = 2/5 Sheet = 2/5 Framework = 1/2 Framework = 1/2

Other ions Quartz (and polymorphs) only minerals with only Si and O Quartz (and polymorphs) only minerals with only Si and O All other silicates are charge balanced by other cations All other silicates are charge balanced by other cations “glue” that holds together silica tetrahedron “glue” that holds together silica tetrahedron

Degree of polymerization depends on availability of Si Degree of polymerization depends on availability of Si Quartz and feldspars (framework): Si-rich environments Quartz and feldspars (framework): Si-rich environments Si/O = ½ Si/O = ½ Olivine (orthosilicate): Si-poor environment Olivine (orthosilicate): Si-poor environment Si/O = ¼ Si/O = ¼

Mafic vs Felsic Mafic – rich in Magnesium and Iron (Ferrum), Si-poor Mafic – rich in Magnesium and Iron (Ferrum), Si-poor E.g. biotite, amphiboles, pyroxenes, and olivine E.g. biotite, amphiboles, pyroxenes, and olivine Commonly dark colored Commonly dark colored Felsic – rich in Si and Al Felsic – rich in Si and Al E.g. Feldspars, Quartz (SiO 2 ), muscovite, feldspathoids E.g. Feldspars, Quartz (SiO 2 ), muscovite, feldspathoids Commonly light colored Commonly light colored