Gabrielite
Encyclopedia
Gabrielite is a rare thallium
sulfosalt mineral with a chemical formula of Tl6Ag3Cu6(As,Sb)9S21 or Tl2AgCu2As3S7.
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.
This region was transformed during the greenschist-garnet/amphibolite facies of metamorphism. Due to this many rare sulfosalts like gabrielite are found in this part of Switzerland.
, which means that the pseudohexagonal shape that this mineral occurs in nature with only has a center of symmetry.
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 (when measured the differences in the properties along the axes). According to Mindat.org, Gabrielite has anisotropic properties. Which means that the velocity of light changes in crystallographic direction, this is easily identifiable in thin section. Another optical property is birefringence (the difference between the two refractive indices, epsilon and omega ray). Gabrielite has very weak anisotropism which is the reason why gabrielite shows little to no birefringence. Mindat.org stated that the mineral gabrielite is not pleochroic (different wavelengths are absorbed in different directions, the color of the mineral varies when rotating the stage in plane polarized light).
Gabrielite is a sulfosalt mineral species occurring as idiomorphic crystals commonly found in cavities of a Triassic
dolomitic
rock. The physical properties of sulfosalts such as gabrielite, the mineral can be used for thermoelectric conducting, and magnetism.
Thallium
Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...
sulfosalt mineral with a chemical formula of Tl6Ag3Cu6(As,Sb)9S21 or Tl2AgCu2As3S7.
It was first reported in 2002 for its occurrence in the Lengenbach quarry
Quarry
A quarry is a type of open-pit mine from which rock or minerals are extracted. Quarries are generally used for extracting building materials, such as dimension stone, construction aggregate, riprap, sand, and gravel. They are often collocated with concrete and asphalt plants due to the requirement...
, Binntal, Valais
Valais
The Valais is one of the 26 cantons of Switzerland in the southwestern part of the country, around the valley of the Rhône from its headwaters to Lake Geneva, separating the Pennine Alps from the Bernese Alps. The canton is one of the drier parts of Switzerland in its central Rhône valley...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, and named after Walter Gabriel, a Swiss
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
mineral photographer.
This region was transformed during the greenschist-garnet/amphibolite facies of metamorphism. Due to this many rare sulfosalts like gabrielite are found in this part of Switzerland.
Structure and properties
Gabrielite has a pseudohexagonal shape and the crystal structure is composed of parallel sheets of ditriagonalization of hexagons which reduces it to a P3 symmetry. According to the American Mineralogist, Gabrielite shows a 6-Fold outline. Gabrielite is part of the triclinic crystal systemCrystal system
In crystallography, the terms crystal system, crystal family, and lattice system each refer to one of several classes of space groups, lattices, point groups, or crystals...
, which means that the pseudohexagonal shape that this mineral occurs in nature with only has a center of symmetry.
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 (when measured the differences in the properties along the axes). According to Mindat.org, Gabrielite has anisotropic properties. Which means that the velocity of light changes in crystallographic direction, this is easily identifiable in thin section. Another optical property is birefringence (the difference between the two refractive indices, epsilon and omega ray). Gabrielite has very weak anisotropism which is the reason why gabrielite shows little to no birefringence. Mindat.org stated that the mineral gabrielite is not pleochroic (different wavelengths are absorbed in different directions, the color of the mineral varies when rotating the stage in plane polarized light).
Gabrielite is a sulfosalt mineral species occurring as idiomorphic crystals commonly found in cavities of a Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
dolomitic
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
rock. The physical properties of sulfosalts such as gabrielite, the mineral can be used for thermoelectric conducting, and magnetism.