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Silicon Tetrahedra by Charina Cameron

Silicon Tetrahedra by Charina Cameron. 4 oxygen atoms 1 silicon atom in the center Forms a 4-sided geometry Each side is like an equilateral triangle Creates a 4- ion. Some Silicate structures. Single tetrahedrons, single chains, double chains, sheets, rings, and 3-D networks.

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Silicon Tetrahedra by Charina Cameron

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  1. Silicon Tetrahedraby Charina Cameron • 4 oxygen atoms • 1 silicon atom in the center • Forms a 4-sided geometry • Each side is like an equilateral triangle • Creates a 4- ion

  2. Some Silicate structures • Single tetrahedrons, single chains, double chains, sheets, rings, and 3-D networks

  3. SINGLE SILICATE TETRAHEDRA crystal • Garnet (red) • Olivine (green) (Fe,Mg)SiO4

  4. SINGLE CHAIN SILICATES • Pyroxene Group [Fe,Mg,Ca,Al silicates]: • Augite (note the near 90o angle of the two cleavages)

  5. DOUBLE CHAIN SILICATES • Amphibole Group [Na,Ca,Fe,Mg,Al silicates w/ H2O]: • The mineral hornblende is common • Nnote the 156 degree angle of the two cleavages

  6. SHEET SILICATES • Muscovite mica[K,Al + H2O] Biotite mica[K,Mg,Fe,Al + H2O] • Note the single perfect cleavage and elastic sheets • Talc Kaolinite (clay) [K,Al + H2O]

  7. ZEOLITE RING SILICATES • Naturalite from North Mountain Basalt Formation

  8. FRAMEWORK SILICATES • Feldspar group: • Most abundant mineral group • Orthoclase (K-feldspar) • Albite (Na-Plagioclase) • Labradorite (Ca-rich Plagioclase) 2 cleavages note twinning lines

  9. FRAMEWORK SILICATES • Quartz (SiO2), the most common mineral: • Chalcedony (SiO2): • microcrystalline quartz • many var. (chert, jasper, flint) quartz crystal rose quartz milky quartz amethyst

  10. FRAMEWORK SILICATES • Hexagonal quartz crystal

  11. FRAMEWORK SILICATES • Amethyst (quartz) geode from the Scots Bay Formation

  12. FRAMEWORK SILICATES • Amethyst (quartz) geode replacing small straight tree trunk surrounded by chert (from Scots Bay Fm)

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