World Library  
Flag as Inappropriate
Email this Article

Arsenopyrite

 

Arsenopyrite

Arsenopyrite
Arsenopyrite, Panasqueira Mine, Portugal
General
Category Sulfide mineral
Formula
(repeating unit)
FeAsS
Strunz classification 02.EB.20
Crystal symmetry Monoclinic 2/m prismatic
Unit cell a = 5.744 Å, b = 5.675 Å, c = 5.785 Å; β = 112.3°; Z = 4
Identification
Color Steel grey to silver white
Crystal habit Acicular, off-square prismatic, stubby; striated; also compact, granular, columnar
Crystal system monoclinic
Twinning Common on {100} and {001}, contact/penetration twinning on {101}
Cleavage 110 (distinct)
Fracture Subconchoidal to rough
Tenacity Brittle
Mohs scale hardness 5.5 - 6
Luster Metallic
Streak Black
Diaphaneity Opaque
Specific gravity 5.9 - 6.2
Optical properties Anisotropism - strong red-violet
Pleochroism Weak, white or bluish tint, faint reddish yellow
Fusibility Yes
Solubility Nitric acid
Other characteristics Garlic odour when struck, greenish tinge when weathered, green staining of wall rocks
References [1][2][3]

Arsenopyrite is an iron arsenic sulfide (FeAsS). It is a hard (Mohs 5.5-6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1.[1] When dissolved in nitric acid, it releases elemental sulfur. 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. 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.

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.[4]

Arsenopyrite also can be associated with significant amounts of gold. Consequently, it serves as an indicator of gold bearing reefs. Many arsenopyrite gold ores are refractory, i.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.

Contents

  • Crystallography 1
  • Related minerals 2
  • See also 3
  • References 4

Crystallography

Arsenopyrite crystal from the Yaogangxian Mine, Hunan, China (size: 2.7 x 2.0 x 1.7 cm)

Arsenopyrite crystallizes in the monoclinic crystal system and often shows prismatic crystal or columnar forms with striations and twinning common. Arsenopyrite may be referred to in older references as orthorhombic, 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 than pyrite. The ion description is imperfect because the material is semiconducting and the Fe-As and Fe-S bonds are highly covalent.[5]

Related minerals

Various transition group metals can substitute for iron in arsenopyrite. The arsenopyrite group includes the following rare minerals:

See also

References

  1. ^ a b Hurlbut, C. S.; Klein, C., 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
  2. ^ http://rruff.geo.arizona.edu/doclib/hom/arsenopyrite.pdf Handbook of Mineralogy
  3. ^ Mindat.org
  4. ^ Mindat Mispickel
  5. ^ Vaugn, D. J.; Craig, J. R. Mineral Chemistry of Metal Sulfides" Cambridge University Press, Cambridge: 1978. ISBN 0-521-21489-0.
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.