Arsenopyrite (

IMA IMA or Ima may refer to: Education * Indian Military Academy, Dehradun * Instituto Miguel Ángel, a school in Mexico City Galleries and museums * Indianapolis Museum of Art, Indiana, US * Institut du Monde Arabe, Paris, France * Islamic Mus ...

symbol A symbol is a mark, Sign (semiotics), sign, or word that indicates, signifies, or is understood as representing an idea, physical object, object, or wikt:relationship, relationship. Symbols allow people to go beyond what is known or seen by cr ...

: Apy) is an iron arsenic

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

(FeAsS). It is a hard ( Mohs 5.5–6) metallic, opaque, steel grey to silver white mineral with a relatively 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 6.1. When dissolved in

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

, it releases elemental

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

. When arsenopyrite is heated, it produces sulfur and arsenic vapor. With 46%

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

content, arsenopyrite, along with

orpiment Orpiment, also known as ″yellow arsenic blende″ is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and may be formed through sublimatio ...

, is a principal

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 ...

of arsenic. When deposits of arsenopyrite become exposed to the atmosphere, the mineral slowly converts into iron arsenates. Arsenopyrite is generally an acid-consuming sulfide mineral, unlike

iron pyrite The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue ...

which can lead to

acid mine drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines and coal mines. Acid rock drainage occurs naturally within some environments as part of the rock weatherin ...

. The

crystal habit In mineralogy, crystal habit is the characteristic external shape of an individual crystal or aggregate of crystals. The habit of a crystal is dependent on its crystallographic form and growth conditions, which generally creates irregularities d ...

, hardness, density, and garlic odour when struck are diagnostic. Arsenopyrite in older literature may be referred to as ''mispickel'', a name of German origin. It is also sometimes referred to as

mundic ''Mundic'' was used from the 1690s to describe a copper ore that began to be smelted at Bristol and elsewhere in southwestern Britain. Smelting was carried out in cupolas, that is reverberatory furnaces using mineral coal. For more details, see ...

, a word derived from

Cornish dialect The Cornish dialect (also known as Cornish English, Anglo-Cornish or Cornu-English) is a dialect of English spoken in Cornwall by Cornish people. Dialectal English spoken in Cornwall is to some extent influenced by Cornish grammar, and often i ...

and which also refers to a copper ore, as well as a form of deterioration in aggregate concrete made with mine tailings. Arsenopyrite also can be associated with significant amounts of

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 ...

. Consequently, it serves as an indicator of gold bearing reefs. Many arsenopyrite gold ores are

refractory In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compound ...

, i.e. the gold is not easily cyanide leached from the mineral matrix. Arsenopyrite is found in high temperature

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 ...

veins, in

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic c ...

s, and in areas of

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 ...

metasomatism Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in the chemical com ...

Crystallography

Arsenopyrite crystallizes in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

crystal system In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices (an infinite array of discrete points). Space groups (symmetry groups ...

and often shows prismatic crystal or columnar forms with

striation Striations means a series of ridges, furrows or linear marks, and is used in several ways: * Glacial striation * Striation (fatigue), in material * Striation (geology), a ''striation'' as a result of a geological fault * Striation Valley, in A ...

s and twinning common. Arsenopyrite may be referred to in older references as

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...

, but it has been shown to be monoclinic. In terms of its atomic structure, each Fe center is linked to three As atoms and three S atoms. The material can be described as Fe³⁺ with the diatomic trianion AsS³⁻. The connectivity of the atoms is more similar to that in

marcasite The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both ...

than

pyrite The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue ...

. The ion description is imperfect because the material is semiconducting and the Fe-As and Fe-S bonds are highly

covalent A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

.Vaugn, D. J.; Craig, J. R. Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. . Arsenopyrite by petrographic microscope NL

Related minerals

Various transition group metals can substitute for iron in arsenopyrite. The arsenopyrite group includes the following rare minerals: * Clinosafflorite: * Gudmundite: * Glaucodot or alloclasite: or * Iridarsenite: * Osarsite or ruarsite: or

References

External links

* {{Authority control Iron minerals Sulfide minerals Arsenic minerals Monoclinic minerals Minerals in space group 14

Crystallography

Related minerals

See also

References

External links