Sperrylite is a

platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...

arsenide In chemistry, an arsenide is a compound of arsenic with a less electronegative element or elements. Many metals form binary compounds containing arsenic, and these are called arsenides. They exist with many Stoichiometry, stoichiometries, and in t ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

with the chemical formula and is an opaque metallic tin white mineral which crystallizes in the isometric system with the

pyrite group The pyrite group of minerals is a set of cubic crystal system minerals with diploidal structure. Each metallic element is bonded to six "dumbbell" pairs of non-metallic elements and each "dumbbell" pair is bonded to six metal atoms. The group is n ...

structure. It forms cubic, octahedral or pyritohedral

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s in addition to massive and reniform habits. It has a

Mohs hardness The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...

of 6–7 and a very high

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of 10.6. It was discovered by the American chemist Francis Louis Sperry in 1888-89 in ore from the Vermillion Mine, part of the

Sudbury Basin The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geology, geological structure in Ontario, Canada. It is among the oldest- and largest-known List of impact structures on Earth, impact structures ...

discoveries, as he did a

fire assay A metallurgical assay is a compositional analysis of an ore, metal, or alloy, usually performed in order to test for purity or quality. Some assay methods are suitable for raw materials; others are more appropriate for finished goods. Raw prec ...

to determine the

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

content of the ore for the Canadian Copper Company who were interested by the property. The most important occurrence of sperrylite is in the

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...

deposit of

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

. It also occurs in the layered

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

complex of the

Bushveld The Bushveld (from Afrikaans: ''bosveld'', Afrikaans: ''bos'' 'bush' and ) is a Tropical and subtropical grasslands, savannas, and shrublands, sub-tropical woodland ecoregion of Southern Africa. The ecoregion straddles the Tropic of Capricorn ...

region of

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

and the Oktyabr'skoye copper-nickel deposit near Noril'sk,

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

Geologic occurrence

Sperrylite is the most common platinum mineral, it generally occurs with a wide array of other unusual minerals, including cooperite [], laurite [], kotulskite [], merenskyite [], iridium-osmium (Ir-Os) alloys, sudburyite [], omeiite [], testibiopalladite [], and niggliite [], to name a few. It does not readily decompose through normal

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

processes and, consequently, has been reported in widely scattered alluvial deposits. It was first found as tiny crystals found with

rhodolite Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It was first described from Cowee Valley, Macon County, North Carolina. The name is derived from the Greek "rhodon" for "rose-like", in common wi ...

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

and

corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock (geology), rock-forming mineral. It is a naturally transparency and translucency, transparent material, but ...

during alluvial gem mining in streams draining Mason Mountain, Macon County, North Carolina (Hidden 1898). Sperrylite has been identified in

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

from sulfide deposits generally associated with layered mafic-ultramafic complexes.

Structure

Sperrylite belongs to the pyrite group of minerals and therefore it shares similar structure and crystal habits with them. Analyses typically show minor amounts of rhodium. Trace copper, iron, and antimony as well as intergrowths with Pt-Fe are reported from some occurrences. Sperrylite crystallizes in Pa3, with a =5.9681(l) A. (Szymański, 1979). It has very similar crystal structure as in platarsite (ideally PtAsS). Sperrylite crystals vary considerably in shape and size and are usually enclosed in a variety of host minerals. They are usually closely associated with basemetal sulfide. They are commonly at the edge and partially enclosed by pentlandite, pyrrhotite or chalcopyrite. Seabrook (2004). Sperrylite is composed of loose aggregate of bright silver cubes, some with octahedral modifications. The grains are mostly anhedral, but a few euhedral grains could also be encountered. Sperrylite is formed by

contact metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of c ...

, as in indicated by the development of

triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three Phase (matter), phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at ...

annealing contacts with

pyrrhotite Pyrrhotite (''Pyrrhus of Epirus, pyrrhos'' in Greek language, Greek meaning "flame-coloured"'')'' is an iron sulfide mineral with the formula Fe(1−x)S (x = 0 to 0.125). It is a nonstoichiometric compound, nonstoichiometric variant of FeS, th ...

grains. The grains of sperrylite are surrounded by later veins of pyrite. Sperrylite is cubic (2/m3) and is typically seen in well-developed cubes or cuboctahedra, some of which are so highly modified that crystal edges and corners appear rounded. (Nicol and Goldschmidt 1903) identified seventeen crystal forms exhibited by sperrylite, including four different trapezohedra, a trisoctahedron, five pyritohedra, and four diploids. Crystals to 2.5 cm have been reported.

Physical properties

Sperrylite is a tin-white mineral known for its brilliant metallic luster, with a grey to black streak. It has indistinct cleavage on and a conchoidal fracture and is brittle. Its hardness is between 6 and 7, and it is quite dense with a calculated specific gravity of 10.78. It has an isometric crystal structure, conchoidal fracture, is non-magnetic and non-radioactive.

Discovery

Sperrylite was first described by H. H. Wells in 1889 from material collected at the Vermilion mine in what is now the

Sudbury district The Sudbury District is a district in Northeastern Ontario in the Canadian province of Ontario. It was created in 1894 from townships of eastern Algoma District and west Nipissing District. In 1973, the Regional Municipality of Sudbury was creat ...

Ontario, Canada Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

. He named it for Francis L. Sperry, chief chemist with the Canadian Copper Company of Sudbury, who collected the original material in 1887 (Mitchell 1985). It occurred in weathered material with colorless transparent

cassiterite Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains ...

[], which is thought to have been derived from the oxidation of stannite [].

References

*Cook, Robert B. (2001) Connoisseur's choice; sperrylite, Talnakh, Noril'sk District, Siberia, Russia. Rocks and Minerals, , Vol. 76, Issue 1 *Szymański, J.T. (1979) the crystal structure of platarsite, Pt (As, S) 2, and a comparison with sperrylite, PtAs2. Canadian Mineralogist: 17: 117–123. *Hidden, W. E. 1898. Occurrence of sperrylite in North Carolina. American Journal of Science 6:381 *Mitchell, R. S. 1985. Who's who in mineral names: Willard Lincoln Roberts and Francis Lewis Sperry. Rocks & Minerals 60:26–28. *Wells, H. H. 1889. Sperrylite, a new mineral. American Journal of Science, vol 37, pp 67–70 *Seabrooke, C.L. 2004. Platinum-group minerals in the Raglan Ni-Cu-(PGE) sulfide deposit, Cape Smith, Quebec, Canada. Canadian mineralogist. Vol. 42, Part 2, pp. 485–497 *Gait, R. I. 1982. Sperrylite from the type locality. Mineralogical Record 13:159-60 *Penfield, S. L. 1889. On the Crystalline form of Sperrylite. American Journal of Science. Vol. 37, pp. 71–73 *Goldschmidt, V. 1903. New forms of Sperrylite. American Journal of Science, Vol. 15, pp. 450–458 {{ores Platinum minerals Arsenide minerals Pyrite group Cubic minerals Minerals in space group 205 Minerals described in 1889

Geologic occurrence

Structure

Physical properties

Discovery

See also

References