Janggunite is a rare manganese oxide mineral with formula Mn5-x(Mn, Fe)1+xO8(OH)6. It is an orthorhombic black mineral containing hydrogen, iron, manganese, and oxygen. It was first described in 1975 for an occurrence in the Janggun mine, Bonghwa-gun, Gyeongsangbuk-do, South Korea and named for the locality.
- Category: Oxide mineral
- Formula: Mn5-x(Mn, Fe)1+xO8(OH)6
- Crystal system: Orthorhombic
- Space group: Pman
Janggunite mineral belongs to Oxide minerals. It has Mohs Hardness between 2-3.
- Color: Black
- Cleavage: Perfect, one direction
- Tenacity: Fragile
- Mohs scale hardness: 2 – 3
- Luster: Dull
- Streak: Brownish black to dark brown
- Specific gravity: 3.59
- Optical properties: Biaxial
Occurrence: Formed at a late stage of oxidation in a cementation zone of a manganese deposit.
Association: Nsutite, todorokite, calcite, rhodochrosite