General Information
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| Chemical Formula: |
(Sc,Y)2Si2O7 |
| Environment: |
Granitic pegmatite rocks. |
| Locality: |
Iveland, Setesdal, Norway. |
| Name Origin: |
Named after the Norwegian engineer, O. Thortveit. |
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Classification
|
| Dana Class: |
55.2.1a.4 (55)Si2O7 Groups, Generally with No Additional Anions (55.2)with cations in [6] coordination (55.2.1a)Thortveitite group |
| Strunz Class: |
VIII/C.01-10 - Silicates [Sorosilicates, with [Si2O7]6-, without anions unfamiliar to tetraheders (Thortveitite - Rowlandite-(Y) series).] |
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Crystallography
|
| Axial Ratios: |
a:b:c =0.7706:1:0.5493 |
| Cell Dimensions: |
a = 6.587, b = 8.547, c = 4.695, Z = 2; beta = 102.65ø V = 257.91 |
| Crystal System: |
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C2/m |
| X Ray Diffraction: |
By Intensity(I/Io): 3.11(1) 3.13(1) 2.93(0.45) |
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Physical Properties
|
| Cleavage: |
[100] Perfect |
| Color: |
brown, grayish black, black, or grayish green. |
| Density: |
3.5 |
| Diaphaniety: |
Translucent to opaque |
| Habits: |
Crystalline - Fine - Occurs as well-formed fine sized crystals., Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Prismatic - Crystals Shaped l ike Slender Prisms (e.g. tourmaline). |
| Hardness: |
6.5 - Pyrite |
| Luminescence: |
Non-fluorescent. |
| Luster: |
Vitreous - Adamantine |
| Streak: |
gray |
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Optical Properties
|
| Optical Data: |
Biaxial (-), a=1.756, b=1.793, g=1.809, bire=0.0530, 2V(Calc)=64, 2V(Meas)=65. |
| Pleochroism (x): |
deep green. |
| Pleochroism (y): |
brownish yellow. |
| Pleochroism (z): |
brownish yellow. |
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Other Information
|
| References: |
NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Ford32) |
| See Also: |
 Athena Mineralogy |
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Frederic Biret |
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Google |
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MinMax |
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École des Mines de Paris |
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