Admontite: Occurrence and Properties

Admontite is a hydrated magnesium borate mineral with formula MgB6O10·7H2O. It was named after Admont in Austria, the place where the mineral was initially discovered, near the original locality.

Occurrence – In a gypsum deposit. Associations: gypsum, anhydrite, hexahydrite, löweite, eugsterite, pyrite, quartz. It is named after Admont, Austria. Its Mohs scale rating is 2 to 3.

Admontite occurs in gypsum deposits. It is often associated with minerals such as gypsum, hexahydrite, loweite, anhydrite, pyrite, eugsterite, and quartz.

General Information:

  • Category: Nesoborates
  • Formula (repeating unit): MgB6O107H2O or MgB6O7(OH)6·4H2O
  • Crystal system: Monoclinic

Identification

  • Color: colorless
  • Cleavage: Absent
  • Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz)
  • Mohs scale: hardness 2 – 3 – Gypsum-Calcite
  • Streak: White
  • Density: 1.82 – 1.87, Average = 1.84
  • Optical properties: Biaxial (-)

It is colorless and transparent with no cleavage. This mineral has a white streak. The fracture on this mineral is conchoidal. It has non-fluorescent luminescence. The density of admontite is 1.82 to 1.87 g/cm3, with a hardness of 2 to 3 – between gypsum and calcite.

Physical Properties of Admontite

  • Density: 1.82 – 1.87, Average = 1.84
  • Diaphaneity: Transparent
  • Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
  • Habit: Euhedral Crystals – Occurs as well-formed crystals showing good external form.
  • Hardness: 2-3 – Gypsum-Calcite
  • Luminescence: Non-fluorescent.

 

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