Gabrielite | |
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General | |
Category | Sulfide mineral |
Formula (repeating unit) | Tl6Ag3Cu6(As,Sb)9S21 |
IMA symbol | Gab [1] |
Strunz classification | 2.HD.60 |
Crystal system | Triclinic |
Crystal class | Pinacoidal (1) (same H-M symbol) |
Space group | P1 |
Unit cell | a = 12.138, b = 12.196 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 |
Density | 5.38 g/cm3 |
Birefringence | weak 470nm R=30.53% 546nm R=29.1% 589nm R=27.94% 650nm R=26.35% |
References | [2] [3] |
Gabrielite is an extremely rare thallium sulfosalt mineral with a chemical formula of Tl6Ag3Cu6(As,Sb)9S21 [2] or Tl2AgCu2As3S7. [3]
It was first reported in 2002 for its occurrence in the Lengenbach quarry, Binntal, Valais, Switzerland. According to Faszination Lengenbach (2008), only 2 specimens are known. A few dozen tiny fragments like the one pictured are circulating few collections. Named after Walter Gabriel (born 1943), a Swiss mineral photographer. [2] [3] 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.
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. [4] Gabrielite is part of the triclinic crystal system, 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. [2] 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 dolomite. The physical properties of sulfosalts such as gabrielite, the mineral can be used for thermoelectric conducting, and magnetism.
Alstonite, also known as bromlite, is a low temperature hydrothermal mineral that is a rare double carbonate of calcium and barium with the formula BaCa(CO
3)
2, sometimes with some strontium. Barytocalcite and paralstonite have the same formula but different structures, so these three minerals are said to be trimorphous. Alstonite is triclinic but barytocalcite is monoclinic and paralstonite is trigonal. The species was named Bromlite by Thomas Thomson in 1837 after the Bromley-Hill mine, and alstonite by August Breithaupt of the Freiberg Mining Academy in 1841, after Alston, Cumbria, the base of operations of the mineral dealer from whom the first samples were obtained by Thomson in 1834. Both of these names have been in common use.
Hutchinsonite is a sulfosalt mineral of thallium, arsenic and lead with formula (Tl,Pb)2As5S9. Hutchinsonite is a rare hydrothermal mineral.
Apachite is a copper silicate mineral with a general formula of Cu9Si10O29·11H2O. The name is associated with the Apache tribe residents of the area near the Christmas copper mine in the Dripping Spring Mountains of Gila County, Arizona, the location where apachite was first described in 1980.
Marrite (mar'-ite) is a mineral with the chemical formula PbAgAsS3. It is the arsenic equivalent of freieslebenite (PbAgSbS3), but also displays close polyhedral characteristics with sicherite and diaphorite. Marrite was named in honor of geologist John Edward Marr (1857–1933) of Cambridge, England.
Jonesite is a mineral with the chemical formula Ba4(K,Na)2[Ti4Al2Si10O36]*6H2O. This mineral is named after Francis Tucker Jones (1905–1993), who discovered the mineral while working as a Research Chemical Microscopist at Berkeley in CA. Jonesite has diffraction symmetry of mmm, which implies an orthorhombic system with all three axes perpendicular to each other and the angles between each axis equal to 90 degrees. In addition to symmetrical properties, Jonesite is a biaxial mineral with birefringence, which is a term to describe the difference between index of refraction. Jonesite is anisotropic, meaning the speed of light changes through the mineral, so the mineral shows color when viewed in crossed polarized light under a microscope. The mineral also has medium relief, which is a measure of how well the mineral stands out when viewed under a microscope in plane polarized light. In addition to being one of the rarest minerals in the Benitoite Gem mine located in California, Jonesite also is the first titanosilicate mineral with a porous double-layered crystal structure. This discovery is important because titanosilicate frameworks have industrial uses in energy companies and are used in containing radioactive waste.
Grandreefite is a rare secondary lead sulfate-fluoride mineral with a general chemical formula, Pb2SO4F2. It is named for the location in which it was discovered in 1989, the Grand Reef Mine in Graham County, Arizona.
Kochite is a rare silicate mineral with chemical formula of (Na,Ca)3Ca2(Mn,Ca)ZrTi[(F,O)4(Si2O7)2] or double that. Kochite is a member of the rosenbuschite group.
Christite is a mineral with the chemical formula TlHgAsS3. It is named after Dr. Charles L. Christ, a member of the U.S. Geological Survey. It usually comes in a crimson red or bright orange color. It has a density of 6.2 and has a rating between 1 and 2 on Mohs Hardness Scale. Christite has an adamantine luster and leaves behind an orange streak. Its crystal system is monoclinic with possible crystal classes of twofold symmetry, mirror plane symmetry, and twofold with a mirror plane. This means it can have radial symmetry, mirror plane symmetry, or mirror plane symmetry perpendicular to the two-fold axis. It is an anisotropic mineral, which means that it exhibits different properties when measured in different directions. In plane polarized light, its color is golden yellow. It is birefringent, which means that it has two distinct indices of refraction. This can be seen when one looks through the microscope with both polars crossed and sees the mineral change colors when it is rotated.
Babefphite is a rare phosphate mineral with the general formula BaBe(PO4)(F,OH). The name is given for its composition (Ba meaning barium, Be meaning beryllium, F meaning fluorine, and P for phosphorus).
Nambulite is a lithium bearing manganese silicate mineral with the chemical formula (Li,Na)Mn4Si5O14(OH). It is named after the mineralogist, Matsuo Nambu (born 1917) of Tohoko University, Japan, who is known for his research in manganese minerals. The mineral was first discovered in the Funakozawa Mine of northeastern Japan, a metasedimentary manganese ore.
Sewardite is a rare arsenate mineral with formula of CaFe3+2(AsO4)2(OH)2. Sewardite was discovered in 1982 and named for the mineralogist, Terry M. Seward (born 1940), a professor of geochemistry in Zürich, Switzerland.
Eveite is a manganese arsenate mineral in the olivenite group. Its chemical formula is Mn2AsO4OH. It is found only in Långban, Filipstad, Värmland, Sweden and at the Sterling Mine in New Jersey, United States. It is a dimorph of sarkinite and is isostructural with adamite. The name, for the biblical "Eve", comes from its structural similarities to adamite and is also a reference to its apple-green color. It can also be pale yellow. Eveite is an orthorhombic mineral, which means it has three crystallographic axes of unequal lengths which are at 90° to one another.
Geerite is a copper sulfide mineral with the chemical formula Cu8S5. The mineral is named after the original collector, Adam Geer, of Utica, New York, US.
Kröhnkite ( Na2Cu(SO4)2•2H2O ) is a rare copper sulfate mineral named after B. Kröhnke who first researched it. Kröhnkite may be replaced by Saranchinaite, the anhydrous form of the mineral, if heated to temperatures above 200 °C (392 °F).
Minyulite is a rare phosphate mineral with a chemical formula of KAl2(PO4)2F·4(H2O).
Kanoite is a light pinkish brown silicate mineral that is found in metamorphic rocks. It is an inosilicate and has a chemical formula of (Mg,Mn2+)2Si2O6. It is a member of pyroxene group and clinopyroxene subgroup.
Fluckite is an arsenate mineral with the chemical formula CaMnH2(AsO4)2·2(H2O).
Enneasartorite is a very rare mineral with formula Tl6Pb32As70S140. It belongs to sartorite homologous series. It is related to other recently approved minerals of the sartorite series: hendekasartorite and heptasartorite. All come from Lengenbach quarry in Switzerland, which is famous for thallium sulfosalts. Enneasartorite is chemically similar to edenharterite and hutchinsonite.
Hendekasartorite is a very rare thallium sulfosalt mineral with formula Tl2Pb48As82S172. It is one of recently approved new members of sartorite homologous series, by enneasartorite and heptasartorite. All new members come from Lengenbach quarry in Switzerland, prolific in terms of thallium sulfosalt minerals. Hendekasartorite is chemically similar to edenharterite and hutchinsonite.
Sartorite is a lead arsenic sulfide with the chemical formula PbAs2S4 and as type locality the Lengenbach Quarry in Legenbach, Binnental, Valais, Switzerland. Historically, sartorite has been thought isomorphic to chalcostibite, emplectite, and zinckenite, but was definitively distinguished from the others in 1939.