Alleghanyite is a moderately rare humite mineral with formula Mn5(SiO4)2(OH)2, belonging to the nesosilicates class. It is a mineral consisting of a pink basic silicate of manganese. It is a monoclinic-prismatic mineral containing hydrogen, manganese, oxygen, and silicon.

In general, its occurrences are related to metamorphic (metamorphosed) manganese deposits. The mineral is named after Alleghany County, North Carolina, US.

General Information

  • Category: Nesosilicates (Humite group)
  • Formula: Mn5(SiO4)2(OH)2,
  • Crystal system: Monoclinic
  • Transparency: Transparent, Translucent.


These chemical properties also depend on the way the mineral atoms are bound in the mineral’s crystal structure. On the basis of the crystallography of minerals, a chemical formula is designed for better interpretation of its structure. Also, it is radioactive as the value of GRapi is 0.00.

  • Formula mass: 492.87 g/mol
  • Color: Brown, bright pink, grayish pink, white
  • Crystal habit: Granular; anhedral to subhedral crystals in matrix
  • Cleavage: None
  • Fracture: Conchoidal
  • Tenacity: Brittle
  • Mohs scale hardness: 5–6
  • Luster: Vitreous
  • Diaphaneity: Transparent to translucent
  • Specific gravity: 4 (means.), 4.11 (calc.)

Alleghanyite occurs in tectonically transported and boudinaged manganese-rich lenses within dolostones and mineralogically distinct layers. It is closely associated with jacobsite, galaxite, chlorite, pyrochroite, manganoan and calcite.


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