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Systematic Mineralogy

Date post: 14-Jan-2016
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Systematic Mineralogy. Description of how minerals are divided into groups Groups based on anions Single anion ( Cl - ) Anion group (SiO 4 4- ) Further divided based on structures. Divisions. Class (anion division) Family (structural division – silicates mostly) - PowerPoint PPT Presentation
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Systematic Mineralogy Systematic Mineralogy Description of how minerals are Description of how minerals are divided into groups divided into groups Groups based on anions Groups based on anions Single anion (Cl Single anion (Cl - ) ) Anion group (SiO Anion group (SiO 4 4- 4- ) ) Further divided based on Further divided based on structures structures
  • Systematic MineralogyDescription of how minerals are divided into groupsGroups based on anionsSingle anion (Cl-)Anion group (SiO44-)Further divided based on structures

  • DivisionsClass (anion division)Family (structural division silicates mostly)Group (structural division)Series (solid solution)Species (individual minerals)Varieties (substituted elements)

  • ExampleCa-grunerite:A Ca-rich varietyOf a mineral speciesIn the cummingtonite-grunerite seriesOf the amphibole groupOf the inosilicate familyOf the silicate class

  • Mineral classAnion or anion gpNative elementsN/AOxidesO2-HydroxidesOH-HalidesCl-, Br-, F-SulfidesS2-SulfatesSO42-CarbonatesCO32-PhosphatesPO43-SilicatesSiO44-

  • SilicatesThe most common group of minerals forming Earths crust25% of all minerals (~1000)40% of rock forming minerals90% of earths crust i.e., those minerals you are likely to find

  • Silicate StructureBasic building block: silica tetrahedronSi4+ with four O2- surrounding itNet charge is 4-Mesodesmic, polymerizationTetrahedron can share oxygen atoms

  • Fig. 11-1Silica Tetrahedron

  • Six groups of silicate mineralsOrthosilicates = NesosilicatesSingle tetrahedronDisilicates = SorosilicatesTwo tetrahedrons share single oxygenRing silicates = Cyclosilicates4, 5, or 6 tetrahedron share two oxygen

  • Chain silicates = Inosilicates2 or 3 oxygen shared, arranged in single or double chainSheet silicates = Phyllosilicates3 oxygen shared in sheetsFramework silicates = TectosilicatesAll 4 oxygen are shared

  • Fig. 11-2Ortho-(Neso)Di-(Soro)Ring(Cyclo)Chain double and single(Ino)Framework(Tecto)Sheet(Phyllo)

  • Z/O ratiosZ = Si tetrahedral sitesCan be other cations, most commonly AlZ/O ratio depends on type of silicateOrtho = 1/4Di = 2/7Ring = 1/3Chain, single = 1/3; double = 4/11Sheet = 2/5Framework = 1/2

  • Other ionsQuartz (and polymorphs) only minerals with only Si and OAll other silicates are charge balanced by other cationsglue that holds together silica tetrahedron

  • Degree of polymerization depends on availability of SiQuartz and feldspars (framework): Si-rich environmentsSi/O = Olivine (orthosilicate): Si-poor environmentSi/O =

  • Mafic vs FelsicMafic rich in Magnesium and Iron (Ferrum), Si-poorE.g. biotite, amphiboles, pyroxenes, and olivineCommonly dark colored Felsic rich in Si and AlE.g. Feldspars, Quartz (SiO2), muscovite, feldspathoidsCommonly light colored