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Arsenopyrite

Veins of Arsenopyrite in rock, Brazil
General
Category Mineral
Chemical formula AsFeS
Identification
Color Steel grey to silver
Crystal habit Acicular, off-square prismatic, stubby or massive; striated
Crystal system monoclinic; ?/m ?/m ?/m
Cleavage 110 (distinct)
Fracture Subconchoidal to rough
Mohs Scale hardness 5. |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes In Mineralogy, shape and size give rise to descriptive terms applied to the typical appearance or habit of Crystals The many terms used by mineralogists A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions In Crystallography, the monoclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three vectors. Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types In the field of Mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a Mineral is broken 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 5 - 6
Luster Metallic
Refractive index Opaque
Pleochroism None
Streak Black
Specific gravity 5. Lustre (or luster) is a description of the way light interacts with the surface of a Crystal, rock, or Mineral. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium Pleochroism is an Optical phenomenon in which grains of a rock appear to be different colors when observed at different angles under a Petrographic microscope. The streak (also called powder color) of a Mineral is the Color of the powder produced when it is dragged across an unweathered surface Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically 9 - 6. 2
Fusibility Yes
Solubility Nitric acid
Other Characteristics Garlic odour when struck, greenish tinge when weathered, green staining of wall rocks

Arsenopyrite is an iron arsenic sulfide (FeAsS). Fusibility is the ease with which a material will Melt. Materials such as solder require a low melting point so that when heat is applied to a joint the solder will melt before Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. The term sulfide ( sulphide in British English) refers to several types of Chemical compounds containing Sulfur in its lowest Oxidation It is a hard (Mohs 5. 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 5-6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6. Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically 1. [1] When dissolved in nitric acid, it releases elemental sulfur. Nitric acid ( H[[nitrate NO3]] also known as Aqua fortis and spirit of nitre, is a highly corrosive and Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 When arsenopyrite is heated, it becomes magnetic and gives off toxic fumes. With 46% arsenic content, arsenopyrite, along with orpiment, is a principal ore of arsenic. Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 Orpiment, As2S3, is a common Monoclinic Arsenic Sulfide mineral An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining When deposits of arsenopyrite become exposed to the atmosphere, usually due to mining, the mineral will slowly oxidize, converting the arsenic into oxides that are more soluble in water, leading to Acid mine drainage. Acid mine drainage ( AMD) or acid rock drainage ( ARD) refers to the outflow of Acidic water from (usually abandoned Metal mines

The crystal habit, hardness, density, and garlic odor when struck are diagnostic. Arsenopyrite in older literature may be referred to as mispickel, a name of German origin[1].

Arsenopyrite also can be associated with significant amounts of gold. Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Consequently it serves as an indicator of gold bearing reefs. Many arsenopyrite gold ores are refractory, i. A refractory is a material that retains its strength at high Temperatures ASTM C71 defines refractories as "non-metallic materials having those chemical and physical e. the gold is not easily liberated from the mineral matrix.

Arsenopyrite is found in high temperature hydrothermal veins, in pegmatites, and in areas of contact metamorphism or metasomatism. Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat Pegmatite is a very coarse-grained Igneous rock that has a grain size of 20 mm or more such rocks are referred to as pegmatitic. Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressure and/or introduction of fluids i Metasomatism is the chemical alteration of a rock by Hydrothermal and other fluids

Crystallography

Arsenopyrite crystallizes in the monoclinic crystal system and often shows prismatic crystal or columnar forms with striations and twinning common. In Crystallography, the monoclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three vectors. A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions Striations means a series of Ridges, furrows or Linear marks and are used in several ways Glacial striation Striation (geology Crystal twinning occurs when two separate crystals share some of the same Crystal lattice points in a symmetrical manner Arsenopyrite may be referred to in older references as orthorhombic, but it has been shown to be monoclinic. In Crystallography, the orthorhombic Crystal system is one of the seven Lattice Point groups Orthorhombic lattices result from stretching 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 than pyrite. The Mineral marcasite, sometimes called white iron pyrite, is Iron Sulfide (FeS2 The ion description is imperfect because the material is semiconducting and the Fe-As and Fe-S bonds are highly covalent. [2]

Related minerals

Various transition group metals can substitute for iron in arsenopyrite. A cobalt-rich variety is known as danaite (named after mineralogist James Dana). Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. James Dwight Dana (February 12 1813 &ndash April 14 1895 was an American Geologist, Mineralogist and Zoologist. The arsenopyrite group includes the following rare minerals:

References

  1. ^ Hurlbut, C. Glaucodot is a Cobalt Iron Arsenic Sulfide mineral with formula (CoFeAsS S. ; Klein, C. , 1985, Manual of Mineralogy, 20th ed. , ISBN 0-471-80580-7
  2. ^ Vaugn, D. J. ; Craig, J. R. Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. ISBN 0521214890.

Dictionary

arsenopyrite

-noun

  1. (mineralogy) A silvery-grey ore of arsenic, a mixed arsenide and sulfide of iron, FeAsS.
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