1 / 31

MOST IMPORTANT MINERAL SUITE: The Silicate Minerals

MOST IMPORTANT MINERAL SUITE: The Silicate Minerals. Si + O = 75% of Crust Silicates make up 95% + of all Rocks SiO 4 : -4 charge Link Corner-To-Corner by Sharing Oxygen atoms. Nesosilicates - Isolated Tetrahedra. Representatives: Garnet Kyanite Olivine Zircon Topaz Staurolite

ganit
Télécharger la présentation

MOST IMPORTANT MINERAL SUITE: The Silicate Minerals

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MOST IMPORTANT MINERAL SUITE: The Silicate Minerals • Si + O = 75% of Crust • Silicates make up 95% + of all Rocks • SiO4: -4 charge • Link Corner-To-Corner by Sharing Oxygen atoms

  2. Nesosilicates - Isolated Tetrahedra • Representatives: • Garnet • Kyanite • Olivine • Zircon • Topaz • Staurolite • Sphene • SiO4 in Formula

  3. Sorosilicates - Paired Tetrahedra • Epidote is the most common example • Lawsonite • Vesuvianite • Si2O7 in Formula

  4. Cyclosilicates - Rings • Beryl (Emerald) • Cordierite • Tourmaline • SinO3n in Formula

  5. What is a Tetrahedron? • In many silicates, Al, Be and other ions occur in tetrahedral coordination • Substitution of Al for Si maintains charge balance in Feldspars • Some mineralogists count all tetrahedra in classifying structure • By this criterion, Beryl and Cordierite are tectosilicates

  6. Inosilicates - Chains Single Chains (Pyroxenes) SiO3 or Si2O6 in Formula

  7. More Realistic Picture

  8. Major Pyroxenes • Ferromagnesian • Enstatite (MgSiO3) – Hypersthene (Mg,Fe)SiO3 • Calcic • Diopside: CaMgSi2O6 • Pigeonite: Ca0.25(Mg,Fe)1.75Si2O6 • Hedenbergite: CaFeSi2O6 • Augite: XYZ2O6

  9. Other Pyroxenes • Sodic • Jadeite: NaAlSi2O6 • Breakdown of Na-Feldspar • High Pressure Metamorphism • Aegerine (Acmite) NaFe3Si2O6 • Spodumene: LiAlSi2O6 • Pegmatite Mineral

  10. Pyroxenes and Cations

  11. Silica Chains and Octahedra

  12. Silica Chains and Octahedra

  13. Two Sites in Pyroxenes

  14. Pyroxenoids • Have single chains but more complex bends to accommodate cations • Lack pyroxene cleavage • Wollastonite (CaSiO3) • Rhodonite and Pyroxmangite (MnSiO3) • Mn is a good match in size and charge for Fe and Mg • Pure Mn true pyroxenes exist • These have complex chains because of variable compositions

  15. Wollastonite CaSiO3

  16. Wollastonite End-On

  17. Rhodonite

  18. Pyroxmangite

  19. Biopyriboles • Biotite = Silica sheets with (Mg,Fe) Sheets in between • Amphiboles and Pyroxenes are strips of Biotite sheets • Biopyribole = Biotite + Pyroxene + Amphibole

  20. Inosilicates - Chains Double Chains (Amphiboles Si4O11 in Formula)

  21. Major Amphiboles • Anthophyllite (Mg,Fe)7Si8O22(OH)2) • Cummingtonite (Fe2Mg5Si8O22(OH)2) -Grunerite (Fe7Si8O22(OH)2) • Tremolite (Ca2Mg5Si8O22(OH)2) – Actinolite (Ca2(Mg,Fe)5Si8O22(OH)2) • Hornblende (X2-3Y5Z8O22(OH)2) • Glaucophane (Na2Mg3Al2Si8O22(OH)2) and Riebeckite (Na2Fe++3,Fe+++2Si8O22(OH)2)

  22. Beyond Amphiboles • There are a few 3-chain and mixed chain silicates • Discovered only in 1970’s • Occur in asbestos

  23. Phyllosilicates – Sheets (Si2O5 in Formula)

  24. Phyllosilicates - Sheets Si2O5 sheets with layers of Mg(OH)2 or Al(OH)3 • Micas • Clay minerals • Talc • Serpentine (asbestos) minerals

  25. Tectosilicates - Three-Dimensional Networks • Quartz Feldspars

  26. Tectosilicates • Quartz and Polymorphs • Feldspars • K-Feldspars (KAlSi3O8) • Plagioclase (NaAlSi3O8)- (CaAl2Si2O8) • Barium Feldspars (BaAl2Si2O8) • Feldspathoids (Foids) • Scapolites • Zeolites

  27. K-Feldspars and Mixtures • K-Feldspars (KAlSi3O8) • Microcline (Slow cooling) • Orthoclase (Faster cooling) • Sanidine (Fastest cooling, High T) • Anorthoclase: Solid solution of K-Feldspar and Albite (NaAlSi3O8) • Perthite: K-Feldspar with exsolved plagioclase • Antiperthite: Plagioclase with exsolved K-Feldspar

  28. Plagioclase • Solid solution of Albite (NaAlSi3O8) and Anorthite (CaAl2Si2O8) • 0-10% An = Albite: Na-Metasomatism • 10-30% An = Oligoclase: Granites • 30-50% An = Andesine: Andesites and Diorite • 50-70% An = Labradorite: Basalt and Gabbro • 70-90% An = Bytownite: Rarest • 90-100% An = Anorthite: Metamorphic

  29. Feldspathoids (Foids) • Fill “ecological niche” of feldspars in Si-poor rocks • Never occur with quartz • Leucite (KAlSi2O6) • Nepheline ((Na,K)AlSiO4)

  30. Scapolites and Relatives • Sodalite (Na8(AlSiO4)6Cl2) • Lazurite (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2) • Scapolite • Marialite = Albite + NaCl • Meionite = Anorthite + CaSO4 or CaCO3

More Related