Gabrielite: Difference between revisions
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| mohs = 1.5 - 2 |
| mohs = 1.5 - 2 |
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| luster = Metallic |
| luster = Metallic |
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| refractive = |
| refractive = 470nm R=30.53% |
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546nm R=29.1% |
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589nm R=27.94% |
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650nm R=26.35% |
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| opticalprop = |
| opticalprop = |
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| birefringence = |
| birefringence = none |
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| pleochroism = |
| pleochroism = none |
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| streak = Blackish red |
| streak = Blackish red |
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| gravity = 5.36 |
| gravity = 5.36 |
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It was first reported in 2002 for its occurrence in the [[Lengenbach]] [[quarry]], [[Binntal]], [[Valais]], [[Switzerland]], and named after Walter Gabriel, a [[Switzerland|Swiss]] mineral photographer.<ref name=Mindat>{{cite web|title=Gabrielite|url=http://www.mindat.org/min-26386.html|publisher=Mindat.org|accessdate=16 September 2010}}</ref><ref name=Webmin/> |
It was first reported in 2002 for its occurrence in the [[Lengenbach]] [[quarry]], [[Binntal]], [[Valais]], [[Switzerland]], and named after Walter Gabriel, a [[Switzerland|Swiss]] mineral photographer.<ref name=Mindat>{{cite web|title=Gabrielite|url=http://www.mindat.org/min-26386.html|publisher=Mindat.org|accessdate=16 September 2010}}</ref><ref name=Webmin/> |
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Gabrielite has a pseudohexagonal shape in nature. Gabrielite is reduces to a p3 symmetry owing to a ditriagonalization of the hexagons. Also, Gabrielite shows a conspicuous 6-Fold outline, through from the distinct striation parallel to the crystallographic a axis.<ref>Graeser, S., ''A New Species of Thallium Sulfosalt from Lengenbach,'' Canadian Mineralogist, 44, 135-141.</ref> |
Gabrielite has a pseudohexagonal shape in nature. Gabrielite is reduces to a p3 symmetry owing to a ditriagonalization of the hexagons. Also, Gabrielite shows a conspicuous 6-Fold outline, through from the distinct striation parallel to the crystallographic a axis.<ref>Graeser, S., ''A New Species of Thallium Sulfosalt from Lengenbach,'' Canadian Mineralogist, 44, 135-141.</ref>. Looking into the optical mineralogy of this mineral we have to define if the mineral is isotropic (uniformity properties in all directions on the axes), or anisotropic (the differences in the properties along the axes. According to mindat.org, Gabrielite has anisotropic properties<sup>1</sup>. Another optical property one should look at is birefringence (the difference between the two refractive indices epsilon and omega ray). Although only uniaxial minerals can be birefringent the mineral Gabrielite is not. Mindat.org also stated that the mineral Gabrielite is not pleochoric (if different wavelengths aare absorbed in different directions, the color of the mineral varies). |
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==References== |
==References== |
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Revision as of 19:05, 8 November 2010
| Gabrielite | |
|---|---|
| General | |
| Category | Sulfide mineral |
| Formula (repeating unit) | Tl6Ag3Cu6(As,Sb)9S21 |
| Crystal system | Triclinic |
| Space group | Triclinic pedial |
| Unit cell | a = 12.138 Å, b = 12.196 Å, c = 15.944 Å; α = 78.537°, β = 84.715°, γ = 60.47°; Z = 6 |
| Identification | |
| Color | Grey to black |
| Crystal habit | Pseudo Hexagonal |
| Twinning | Common, with (100) as twin plane |
| Cleavage | Perfect on {001} |
| Fracture | uneven |
| Mohs scale hardness | 1.5 - 2 |
| Luster | Metallic |
| Streak | Blackish red |
| Diaphaneity | Opaque |
| Specific gravity | 5.36 |
| Refractive index | 470nm R=30.53%
546nm R=29.1%
589nm R=27.94%
650nm R=26.35% |
| Birefringence | none |
| Pleochroism | none |
| References | [1][2] |
Gabrielite is a rare thallium sulfosalt mineral with a chemical formula of Tl6Ag3Cu6(As,Sb)9S21[1] or Tl2AgCu2As3S7.[2]
It was first reported in 2002 for its occurrence in the Lengenbach quarry, Binntal, Valais, Switzerland, and named after Walter Gabriel, a Swiss mineral photographer.[1][2]
Gabrielite has a pseudohexagonal shape in nature. Gabrielite is reduces to a p3 symmetry owing to a ditriagonalization of the hexagons. Also, Gabrielite shows a conspicuous 6-Fold outline, through from the distinct striation parallel to the crystallographic a axis.[3]. Looking into the optical mineralogy of this mineral we have to define if the mineral is isotropic (uniformity properties in all directions on the axes), or anisotropic (the differences in the properties along the axes. According to mindat.org, Gabrielite has anisotropic properties1. Another optical property one should look at is birefringence (the difference between the two refractive indices epsilon and omega ray). Although only uniaxial minerals can be birefringent the mineral Gabrielite is not. Mindat.org also stated that the mineral Gabrielite is not pleochoric (if different wavelengths aare absorbed in different directions, the color of the mineral varies).
References
- ^ a b c "Gabrielite". Mindat.org. Retrieved 16 September 2010.
- ^ a b c Webmineral data
- ^ Graeser, S., A New Species of Thallium Sulfosalt from Lengenbach, Canadian Mineralogist, 44, 135-141.
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