Sperrylite is a platinum

Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

 arsenide

Arsenide

Arsenide is an arsenic anion with the charge −3. The trianion is formed by the reduction of arsenic by three electrons. For example heating arsenic powder with excess sodium gives sodium arsenide . The anions have no existence in solution since they are extremely basic...

 mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 with formula: PtAs₂ and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite

Pyrite

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...

 group structure. It forms cubic, octahedral or pyritohedral crystal

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...

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

Mohs scale of mineral hardness

The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...

 of 6 - 7 and a very high specific gravity

Relative density

Relative density, or specific gravity, is the ratio of the density of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water...

 of 10.6.

It was discovered by Francis Louis Sperry, an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 chemist, in 1889 at Sudbury.

The most important occurrence of Sperrylite is in the nickel

Nickel

Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 ore

Ore

An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

 deposit of Sudbury Basin

Sudbury Basin

The Sudbury Basin, also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geologic structure in Ontario, Canada. It is the second-largest known impact crater or astrobleme on Earth, as well as one of the oldest....

 in Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It also occurs in the layered igneous complex of the Bushveld

Bushveld

The Bushveld is a sub-tropical woodland ecoregion of Southern Africa that encompasses most of Limpopo Province and a small part of the North West Province of South Africa, the Central and North-East Districts of Botswana and the Matabeleland South and part of th Matabeleland North provinces of...

 region of South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 and the Oktyabr'skoye copper-nickel deposit of the Eastern-Siberian Region, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

.

Geologic occurrence

Sperrylite is the most common platinum mineral, it generally occurs with a wide array of other unusual minerals, including cooperite

Cooperite

Cooperite is a grey mineral consisting of platinum sulfide , generally in combinations with sulfides of other elements such as palladium and nickel . Its general formula is S. It is a dimorph of braggite....

 [(Pt,Pd,Ni)S], laurite

Laurite

Laurite is an opaque black, metallic ruthenium sulfide mineral with formula: RuS2. It crystallizes in the isometric system. It is in the pyrite structural group. Though rare, it occurs in many parts of the world....

 [RuS₂], kotulskite [Pd(Te,Bi)], merenskyite

Merenskyite

Merenskyite is a rare telluride / bismuthinide mineral with formula: 2. It is an opaque white to light gray metallic mineral that occurs as inclusions within other minerals such as chalcopyrite...

 [(Pd,Pt)(Te,Bi)₂], iridium-osmium (Ir-Os) alloy

Alloy

An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

s, sudburyite [(Pd,Ni)Sb], omeiite [(Os,Ru)As₂], testibiopalladite [PdTe(Sb,Te)], and niggliite [PtSn], to name a few. It does not readily decompose through normal weathering

Weathering

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

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

Rhodolite

Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It is found in Cowee Valley, Macon County, North Carolina. The name is derived from the Greek for "rose-like", in common with many pink mineral types , but rhodolite itself is not officially recognised...

 garnet

Garnet

The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...

 and corundum

Corundum

Corundum is a crystalline form of aluminium oxide with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red...

 during alluvial gem

Gemstone

A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...

 mining in streams draining Mason Mountain, Macon County, North Carolina

Macon County, North Carolina

- Geographic features :Of the in Macon County, are federal lands that lie within the Nantahala National Forest and are administered by the United States Forest Service. Of the of USFS land, lie in the Highlands Ranger District and the remaining lie in the Wayah Ranger District...

 (Hidden 1898). Sperrylite has been identified in Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 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 [Pt(As,S)₂]. 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, as in indicated by the development of triple point

Triple point

In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium...

 annealing contacts with pyrrhotite

Pyrrhotite

Pyrrhotite is an unusual iron sulfide mineral with a variable iron content: FeS . The FeS endmember is known as troilite. Pyrrhotite is also called magnetic pyrite because the color is similar to pyrite and it is weakly magnetic...

 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 comers 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.

Cell dimensions	a = 5.967, Z = 4; V = 212.46 Den(Calc)= 10.78
Crystal system	Isometric - Diploidal H-M Symbol (2/m 3) Space Group: P a3
X ray diffraction	By Intensity(I/Io): 1.801(1), 1.148(0.7), 2.98(0.6)
Forms	[1 0 2] [1 1 1] [1 0 0]

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 {001} 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 cystal system, Conchoidal fracture, 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

Sudbury District, Ontario

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....

, Ontario, Canada. 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

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...

 [SnO₂], which is thought to have been derived from the oxidation of stannite

Stannite

Stannite is a mineral, a sulfide of copper, iron, and tin. The chemical formula Cu2FeSnS4. Zinc commonly occurs with the iron and trace germanium may be present. Stannite is used as an ore of tin, consisting of approximately 28% tin, 13% iron, 30% copper, 30% sulfur by mass...

[Cu₂(Fe,Zn)SnS₄].