Atheneite is a rare

palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...

, mercury arsenide mineral with the chemical formula associated with palladium–

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...

deposits. Its composition parallels that of arsenopalladinite (), isomertieite () and meritieite-II () (Cabral, 2002).

Discovery and occurrence

It was discovered in 1974 by A.M. Clark, A.J. Criddle, and E.E. Fejer in the Minas Gerais mine in the town of

Itabira Itabira is a Brazilian municipality and a major city in the state of Minas Gerais. The city belongs to the Belo Horizonte metropolitan area mesoregion and to the Itabira microregion. It is currently the twenty-fourth largest city in the state in ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

(Clark, 1974). Atheneite was also found in 1982 during a major gold rush at

Serra Pelada Serra Pelada (English: "Naked Mountain") is a Brazilian village, district of the municipality of Curionópolis, in the southeast of Pará. Serra Pelada was a large gold mine in Brazil south of the mouth of the Amazon River. The mine was made in ...

in northern Brazil. Since then it has been found in the northern region of Para, Brazil, the northern region of Russia, and the

Limpopo Limpopo is the northernmost province of South Africa. It is named after the Limpopo River, which forms the province's western and northern borders. The capital and largest city in the province is Polokwane, while the provincial legislature is ...

province of South Africa (Cabral, 2002; Trabaev, 1995). Its name is derived from the Greek goddess

Pallas Athena Athena or Athene, often given the epithet Pallas, is an ancient Greek goddess associated with wisdom, warfare, and handicraft who was later syncretized with the Roman goddess Minerva. Athena was regarded as the patron and protectress of v ...

for its association with palladium-gold deposits. It was first found in concentrates from gold washings in Brazil with intergrowths of arsenopalladinite (Fleischer, 1974). Hematite was also found in intergrowths with atheneite, and is interpreted as being the product of a low temperature, hydrothermal origin.

Structure

Atheneite crystallizes in the

hexagonal crystal system In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crysta ...

with

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

''P''2m and a point grouping of m2. It has a ditrigonal dipyramidal crystal form. This mineral does not extinguish under crossed polars, showing bright anisotropic colors from purple-brown to dark grey (Fleischer, 1974). These birefringence colors are of the first order. The atomic structure of atheneite is very similar to that of the hexagonal structure carbons that make up graphite.

Physical properties

Atheneite has a metallic luster and its color ranges from white/gray to blue/gray tint. Its

Mohs hardness scale The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...

is 4.5-5. The

Vickers hardness test 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 t ...

puts this mineral at a 48. Atheneite also has a

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...

of 10.2. When placed in a reflected light, it gives off a white light with a yellowish hue and shows very weak reflectance

pleochroism Pleochroism (from Greek πλέων, ''pléōn'', "more" and χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light. Backgrou ...

in oil (Fleischer, 1974).

References

{{Reflist * New mineral names, Fleischer, Michael In: American Mineralogist, 1974, vol. 59, Issue 11-12, pp 1330–1332. * Palladium and Platinum Minerals From the Serra Pelada Au-Pd-Pt Deposit, Carajas Mineral Province, Northern Brazil, Cabral, Alexandre Raphael; Lehmann, Bernd; Dwitdo-Ribeiro, Ribeiro; Cravo Costa; Henrique, Carlos: The Canadian Mineralogist, 2002, vol. 40, pp1451–1463. * Palladium Gold and Palladium Arsenide-Antimonide Minerals from Congo Soco Iron Ored Mine, Quadrilatero Ferritero, Minas Gerais Brazil, Cabral, A.R.: Kwitko, R: Jones R.D. Applied earth science, vol.111, num. 1, April 2002, pp. 74–80. * Palladium arsenide-antimonides from Itabira, Minas Gerais, Brazil, Clark, A. M. In: Mineralogical Magazine and Journal of the Mineralogical Society, 1974, Vol. 39, Issue 305, pp. 528–543 * New Gold-Palladium Type of Mineralization in the Kozhim Region of Circumpolar Ural (Russia). Trabaev, M.B.; Kuznetsov, S.K.; Moralev, G.V.; Soboleva, A.A.; Laputina, I.P. Geology of Ore Deposits, 1995. Arsenide minerals Mercury minerals Palladium minerals Hexagonal minerals Minerals in space group 189