Manganvesuvianite: Properties and Occurrences

Manganvesuvianite is a tetragonal-dipyramidal deep maroon red mineral containing aluminum, calcium, hydrogen, iron, magnesium, manganese, oxygen, and silicon. It is a rare mineral with formula Ca19Mn3+(Al, Mn3+, Fe3+)10(Mg, Mn2+)2(Si2O7)4(SiO4)10 O(OH)9. It is a member of the vesuvianite group and is the manganese analog of vesuvianite. The mineral is red to nearly black in color.

Discovered in South Africa and described in 2002, it was so named for the prevalence of manganese in its composition and its relation to vesuvianite.

General Information

  • Category: Sorosilicates
  • Formula: Ca19Mn3+(Al,Mn3+,Fe3+)10(Mg,Mn2+)2(Si2O7)4(SiO4)10 O(OH)9.
  • Crystal system: Tetragonal
  • Crystal class: Dipyramidal (4/m) (same H-M symbol)
  • Color: Deep red-brown, red, nearly black.

Properties

Manganvesuvianite forms as red to lilac and black prismatic crystals. Its crystals occur as long prisms up to 1.5 cm. Small crystals are transparent and red to lilac in color; large crystals are opaque and nearly black in color with dark-red internal reflections. Strongly zoned crystals less than 0.2 mm (0.0079 in) in size constitute rock-forming manganvesuvianite.

  • Cleavage: None observed
  • Fracture: Conchoidal
  • Mohs scale hardness: 6 to 7
  • Luster: Vitreous
  • Streak: White
  • Diaphaneity: Transparent, translucent, opaque
  • Optical properties: Uniaxial (-)

Occurrence

It was named for the relationship to vesuvianite and for the dominance of manganese in the chemical composition. As of 2012, manganvesuvianite has been found at two locations in South Africa. It formed at temperatures of 250 to 400°C (482 to 752°F) by the hydrothermal alteration of sedimentary and metamorphic manganese ores. Crystallization occurred in fault planes and lenticular bodies in the ore bed or by filling veins and vugs.

Manganvesuvianite has been found in association with calcite, manganese-poor grossular, hydrogrossular-henritermierite, mozartite, serandite-pectolite, strontiopiemontite-tweddillite, and xonotlite. Also found in the Harstigen mine in Varmland, Sweden.

 

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