Nsutite: Properties and Occurrences

Nsutite is a manganese oxide mineral with formula: (Mn4+1-xMn2+xO2-2x(OH)2x where x = 0.06-0.07). It is a major manganese oxide that occurs in mineable quantities in several terrestrial localities and has also been reported to occur in manganese nodules. It is found in most large manganese deposits and was first discovered in Nsuta, Ghana. Since then, it has been found worldwide.

Nsutite is used as a cathode in zinc-carbon batteries, but synthetic manganese oxide is gradually replacing it. It has industrial importance since the intergrowth mineral and its synthetic analogue (γ-MnO2) are used as the cathodic material in dry-cell batteries. The effectiveness of the material in batteries varies widely, and the physical cause of this variation is poorly understood.

General Information

  • Category: Oxide minerals
  • Formula: (repeating unit) (Mn4+1-xMn2+xO2-2x(OH)2x where x = 0.06-0.07
  • Crystal system: Hexagonal
  • Colour: grey-black
  • Member of: Ramsdellite Group

Properties

Nsutite is a dull mineral with a hardness of 6.5-8.5 and an average specific gravity of 4.45. It is used as a cathode in zinc-carbon batteries, but synthetic manganese oxide is gradually replacing it.

  • Streak: grey-black
  • Hardness: 6½ – 8 on Mohs scale
  • Cleavage: None Observed
  • Density: 4.24 – 4.67, Average = 4.45
  • Diaphaneity: Opaqu
  • Habit:  Massive – Uniformly indistinguishable crystals forming large masses.
  • Luster: Earthy (Dull)
  • Streak: black

Occurrences – Thought to be supergene, formed under alkaline oxidizing conditions deficient in barium and potassium.

It is found in most large manganese deposits and was first discovered in Nsuta, Ghana. Since then, it has been found worldwide. Nsutite occurs as opaque, dark gray to black, porous to dense aggregates; G is variable from 4.24-4.67; H = 8.5 (Moh’s scale) and 1150 (Vicker’s scale). It shows a strong, diagnostic x-ray diffraction line at 1.64 Å.

Association: Pyrolusite, cryptomelane, roman`echite, chalcophanite, other Mn oxides, rhodochrosite, quartz, goethite.