Jarosewichite: Properties and Occurrences

Jarosewichite is a rare manganese arsenate mineral with formula: Mn23+Mn3+(AsO4)(OH)6. It was first described in Franklin, New Jersey which is its only reported occurrence. Its chemical composition and structure are similar to chlorophoenicite. This mineral is orthorhombic with 2/m2/m2/m point group. Its crystals are prismatic or barrel-shaped. The color of jarosewichite is dark red to black. It has the subvitreous luster of fracture surfaces and reddish-orange streak. This mineral occurs with flinkite, franklinite, andradite, and cahnite.

General Information

  • Category: Arsenate mineral
  • Formula: Mn23+Mn3+(AsO4)(OH)6
  • Crystal system: Orthorhombic
  • Crystal class: Disphenoidal (222)

Fig: Jarosewichite – a manganese arsenate mineral 

Properties

The color of jarosewichite in nature is very dark red, sometimes black. It has the subvitreous luster of fracture surfaces and reddish-orange streak. The Mohs scale of hardness is almost 4. The density is 3.66(4) g/cm3, which is determined by heavy liquid techniques. This value is very similar to the calculated result of 3.70 g/cm3.

  • Color: Very dark red
  • Cleavage: None observed
  • Fracture: Irregular – uneven
  • Tenacity: Brittle
  • Mohs scale hardness: 4
  • Luster: Subvitreous
  • Streak: Reddish orange
  • Diaphaneity: Translucent through thin edges
  • Specific gravity: 3.66
  • Optical properties: Biaxial (-)

Geologic occurrence

Jarosewichite was first found by David K. Cook in Franklin, Sussex County, New Jersey. It always occurs with flinkite, franklinite, andradite, and cahnite. The mine specimen has a stratified crust of vugs from metamorphosed zinc orebody. There are some small crystals of hausmannite, allactite, and cahnite on the vugs, which formed with jarosewichite.

Association: Flinkite, cahnite, allactite, hausmannite, andradite, franklinite.

 

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