Gabrielite is a rare

thallium Thallium is a chemical element with the symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes an ...

sulfosalt mineral Sulfosalt minerals are sulfide minerals with the general formula , where *A represents a metal such as copper, lead, silver, iron, and rarely mercury, zinc, vanadium *B usually represents semi-metal such as arsenic, antimony, bismuth, and rarely ...

with a chemical formula of or .Webmineral data
/ref> It was first reported in 2002 for its occurrence in the Lengenbach

quarry A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their envir ...

, Binntal,

Valais Valais ( , , ; frp, Valês; german: Wallis ), more formally the Canton of Valais,; german: Kanton Wallis; in other official Swiss languages outside Valais: it, (Canton) Vallese ; rm, (Chantun) Vallais. is one of the 26 cantons forming the S ...

, Switzerland, and named after Walter Gabriel (born 1943), 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.

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.Graeser, S., Topa, D., Balić-Žunić, T., and Makovicky, E. (2006) A New Species of Thallium Sulfosalt from Lengenbach, Binntal, Switzerland. Canadian Mineralogist, 44, 135-140. Gabrielite is part of the

triclinic 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal i ...

crystal system In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices. Space groups are classified into crystal systems according to their poin ...

, 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

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

. The physical properties of sulfosalts such as gabrielite, the mineral can be used for thermoelectric conducting, and magnetism.

References

{{reflist Thallium minerals Silver minerals Sulfosalt minerals Copper(I) minerals Arsenic minerals Antimony minerals Triclinic minerals Minerals in space group 2 Minerals described in 2002