Galaxite: Properties and Occurrences

Galaxite, also known as ‘mangan-spinel’ is an isometric mineral belonging to the spinel group of oxides with the ideal chemical formula Mn2+Al2O4. It is a brownish-red spinel mineral found in carbonate-rich metamorphosed manganese ore deposits. Galaxite is the manganese (Mn) rich endmember of the aluminum (Al) series of the spinel group. It is sometimes used as a gemstone.

General Information

  • Category: Oxide minerals (Spinel group)
  • Formula: MnAl2O4.
  • Crystal system: Cubic
  • Crystal class: Hexoctahedral (m3m)

Fig: Galaxite

Properties

Galaxite generally occurs as small granular aggregates with a red-brownish tone. It has a vitreous luster and leaves a brownish-red streak. It is rated 7.5 on the Mohs Scale.

  • Color: Black, red-brown, red to yellow
  • Crystal habit: Octahedra and rounded grains and exolution blebs
  • Cleavage: Indistinct to none
  • Fracture: Conchoidal to irregular
  • Tenacity: Brittle
  • Mohs scale hardness: 7.5
  • Luster: Vitreous
  • Streak: Red-brown
  • Diaphaneity: Opaque; may be translucent in thin section
  • Specific gravity: 4.234
  • Optical properties: Isotropic

Occurrence

It was first described in 1932 for an occurrence at Bald Knob, Alleghany County, North Carolina near its namesakes, the town of Galax, Virginia, named after the plant galax or wandflower which grows in the area.

It occurs in carbonate-rich metamorphosed manganese ore deposits. It occurs associated with alleghanyite, rhodonite, sonolite, spessartine, tephroite, kutnohorite, manganhumite, jacobsite, kellyite and alabandite in the Bald Knob area. Associated minerals include katoptrite, magnetite, manganostibite, magnussonite, tephroite, manganhumite, and manganosite in the Brattfors mine area of Nordmark, Värmland, Sweden.

 

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