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Tourmaline general formula

Tourmaline general formula. XY 3 Z 6 (BO 3 ) 3 Si 6 O 18 (OH) 3 (OH,F) X = Na, Ca, K Y = Mg, Fe, Mn, Li, Cr +3, V +3 , Ti, Al Z = Al, Mg, Fe, V +3 , Cr +3. Tourmaline. Elbaite Na(Li,Al) 3 Al 6 (BO 3 ) 3 Si 6 O 18 (OH) 4. Dravite NaMg 3 (Al,Fe) 6 (BO 3 ) 3 Si 6 O 18 (OH) 4.

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Tourmaline general formula

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  1. Tourmaline general formula XY3Z6(BO3)3Si6O18(OH)3(OH,F) X = Na, Ca, K Y = Mg, Fe, Mn, Li, Cr+3, V+3, Ti, Al Z = Al, Mg, Fe, V+3, Cr+3

  2. Tourmaline

  3. Elbaite Na(Li,Al)3Al6(BO3)3Si6O18(OH)4

  4. Dravite NaMg3(Al,Fe)6(BO3)3Si6O18(OH)4

  5. Schorl NaFe3(Al,Fe)6(BO3)3Si6O18(OH)4

  6. Uvite Ca(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH)4

  7. Buergerite NaFe3Al6(BO3)3Si6O18(OH)3F

  8. Some tourmaline end members Elbaite Na(Li,Al)3Al6(BO3)3Si6O18(OH)4 Dravite NaMg3(Al,Fe)6(BO3)3Si6O18(OH)4 Schorl NaFe3(Al,Fe)6(BO3)3Si6O18(OH)4 Uvite Ca(Mg,Fe)3Al5Mg(BO3)3Si6O18(OH)4 Buergerite NaFe3Al6(BO3)3Si6O18(OH)3F Foitite Na(Fe,Al)3Al6(BO3)3Si6O18(OH)4 Liddicoatite Ca(Li,Al)3Al6(BO3)3Si6O18(OH,F)4 Rossmanite LiAl3Al6(BO3)3Si6O18(OH)4 Feruvite (Ca,Na)(Fe,Mg,Ti)3(Al,Fe)6(BO3)3Si6O18(OH)4 Chromdravite NaMg3Cr6(BO3)3Si6O18(OH)4 Olenite NaAl3Al6(BO3)3Si6O18(OH)4 Povondraite NaFe3Fe6(BO3)3Si6O18(OH)4

  9. Physical properties of tourmaline Density (g/cm3) 3.0 (elbaite) - 3.2 (schorl) Hardness 7 - 7.5 Refractive indices 1.62, 1.68 (elbaite) Birefringence 0.014 - 0.032 Piezoelectric and pyroelectric Often displays color zoning

  10. Unit cell data for tourmaline Space group R3m a = 15.917 Å c = 7.189 Å V = 455.33Å3 a = 90° g = 120° Z = 3

  11. Atomic positional parameters of tourmaline X 0 0 .8408 Y .06148 .93852 .4269 Z .26126 .29749 .4534 Si .18986 .19175 .0640 B .8904 .1096 .6113 H .1264 .8736 .6876 O1 0 0 .2929 O2 .93958 .06042 .5795 O3 .13052 .86948 .5538 O4 .90697 .09303 -.0087 O5 .09146 .90854 -.0292 O6 .18417 .19430 .2874 O7 .28499 .28554 -.0137 O8 .26962 .20899 .6249

  12. Tourmaline: looking down (001)

  13. Tourmaline: looking down (001)

  14. Solid solution between tourmaline end members

  15. Chemistry of tourmaline From Dyar et al. B: 2.86 - 3.26 pfu Li: 0.0 - 1.44 pfu F: 0.0 - 0.91 pfu H: 0.0 - 3.76 pfu Si: 5.6 - 6.19 pfu Fe+3/Total Fe: 0.0 - 1.0 Fe+2 occupies 3 different Y sites. Fe+2 and Fe+3 can be in both Y and Z octahedral sites. There may also be a small amount of [4]Fe+3

  16. Tourmaline structure is flexible • Tetrahedral bond angles inversely proportional to alkali-O bond length • Distortion of silica ring (ditrigonality) inversely proportional to 9b octahedron angle variance • Unit cell dimensions increase as 9b and 18c octahedra dimensions increase From Foit et al.

  17. Uses of tourmaline • Gemstones • Electronics (pyroelectric and piezoelectric)

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