Frankdicksonite
Encyclopedia
Frankdicksonite is a halide mineral
with the chemical formula Ba
F
2 which corresponds to the chemical compound barium fluoride
. It occurs in the Carlin gold deposit of Eureka County, Nevada
as cubic crystals sized between 0.1 and 4 mm, and is of hydrothermal
origin. Its only associated mineral is quartz
and the frankdicksonite crystals are always completely encapsulated in it. Frankdicksonite has fluorite
crystal structure with a cubic symmetry and the lattice constant a = 619.64 pm. Its Vickers hardness on the {111} cleavage crystal faces varies between 88 and 94 kg/mm2 and is close to that of the synthetic barium fluoride (95 kg/mm2). Its refractive index
(1.475) is almost identical to that of BaF2 (1.474). Under electron irradiation, it emits strong blue cathodoluminescence
. The major impurity in frankdicksonite is strontium
with concentrations up to 0.5% by weight. Also present are silicon
(0.02%) and magnesium
(0.0015%); other impurities have concentrations below 0.0015%.
Although synthetic barium fluoride has been commonly known from at least 1846, it had not been found in nature. The natural existence of barium fluoride was predicted by Michael Fleischer in 1970. Later in the same year, the mineral was discovered by Arthur S. Radtke and named after Frank W. Dickson (1922- ), professor of Geochemistry
at Stanford University
in recognition of his contributions to geology and geochemistry of low-temperature ore deposits. Frankdicksonite was officially recognized by the Commission of New Minerals and Mineral Names in 1974.
Halide mineral
The halide mineral class include those minerals with a dominant halide anion . Complex halide minerals may also have polyatomic anions in addition to or that include halides.Examples include the following:*Halite NaCl*Sylvite KCl...
with the chemical formula Ba
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
F
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...
2 which corresponds to the chemical compound barium fluoride
Barium fluoride
Barium fluoride is a chemical compound of barium and fluorine. It is a solid which can be a transparent crystal. It occurs in nature as the mineral frankdicksonite.-Structure:...
. It occurs in the Carlin gold deposit of Eureka County, Nevada
Eureka County, Nevada
Eureka County is a county located in the U.S. state of Nevada. As of the 2000 census, the population was 1,651. Its county seat is Eureka.Eureka County is part of the Elko Micropolitan Statistical Area.-History:...
as cubic crystals sized between 0.1 and 4 mm, and is of hydrothermal
Hydrothermal circulation
Hydrothermal circulation in its most general sense is the circulation of hot water; 'hydros' in the Greek meaning water and 'thermos' meaning heat. Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust...
origin. Its only associated mineral is quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and the frankdicksonite crystals are always completely encapsulated in it. Frankdicksonite has fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
crystal structure with a cubic symmetry and the lattice constant a = 619.64 pm. Its Vickers hardness on the {111} cleavage crystal faces varies between 88 and 94 kg/mm2 and is close to that of the synthetic barium fluoride (95 kg/mm2). Its refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
(1.475) is almost identical to that of BaF2 (1.474). Under electron irradiation, it emits strong blue cathodoluminescence
Cathodoluminescence
Cathodoluminescence is an optical and electrical phenomenon whereby a beam of electrons is generated by an electron gun and then impacts on a luminescent material such as a phosphor, causing the material to emit visible light. The most common example is the screen of a television...
. The major impurity in frankdicksonite is strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
with concentrations up to 0.5% by weight. Also present are silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
(0.02%) and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
(0.0015%); other impurities have concentrations below 0.0015%.
Although synthetic barium fluoride has been commonly known from at least 1846, it had not been found in nature. The natural existence of barium fluoride was predicted by Michael Fleischer in 1970. Later in the same year, the mineral was discovered by Arthur S. Radtke and named after Frank W. Dickson (1922- ), professor of Geochemistry
Geochemistry
The field of geochemistry involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks, water, and soils, and the cycles of matter and energy that transport the Earth's chemical components in time and space, and...
at Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
in recognition of his contributions to geology and geochemistry of low-temperature ore deposits. Frankdicksonite was officially recognized by the Commission of New Minerals and Mineral Names in 1974.