Frankdicksonite is a

halide mineral Halide minerals are those minerals with a dominant halide anion (, , and ). Complex halide minerals may also have Polyatomic ion, polyatomic anions. Examples include the following: *Atacamite *Avogadrite (K,Cs)BF *Bararite (β) *Bischofite * ...

with the chemical formula Ba F₂ which corresponds to the chemical compound barium fluoride. It occurs in the Carlin gold deposit of

Eureka County, Nevada Eureka County is a county in the U.S. state of Nevada. As of the 2020 census, the population was 1,855, making it the second-least populous county in Nevada. Its county seat is Eureka. Eureka County is part of the Elko Micropolitan Statist ...

as cubic crystals sized between 0.1 and 4 mm, and is of

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

origin. Its only associated mineral is

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

and the frankdicksonite crystals are always completely encapsulated in it. Frankdicksonite has

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...

crystal structure with a cubic symmetry and the lattice constant ''a'' = 619.64 pm. Its

Vickers hardness The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness ...

on the 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 In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

(1.475) is almost identical to that of BaF₂ (1.474). Under electron irradiation, it emits strong blue

cathodoluminescence Cathodoluminescence is an optical and electromagnetic phenomenon in which electrons impacting on a luminescent material such as a phosphor, cause the emission of photons which may have wavelengths in the visible spectrum. A familiar example i ...

. The major impurity in frankdicksonite is

strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...

with concentrations up to 0.5% by weight. Also present are

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

(0.02%) and

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

(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 (born 1922), professor of

Geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...

Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...

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.

References

{{reflist Barium minerals Fluorine minerals Cubic minerals Minerals in space group 225