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.
- 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.