Janggunite is a rare manganese oxide mineral typically found as fibrous or radiating crusts within manganese-rich ore deposits. It is often identified by its dark brown streak and submetallic luster in specimens associated with rhodochrosite.
Is this janggunite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch janggunite with a known reference. Janggunite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Janggunite leaves a dark brown streak.
- 3Read the lusterHold the specimen under a strong light. Janggunite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, radiating aggregates, crusts.
Often confused with
Janggunite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Hausmannite is the harder of the two (Mohs 5-5.5 vs. 3-4); streak differs — Janggunite leaves dark brown, Hausmannite leaves brownish-red.
How to tell apart: Romanèchite is the harder of the two (Mohs 5-6 vs. 3-4); streak differs — Janggunite leaves dark brown, Romanèchite leaves shiny brownish black; luster reads submetallic on Janggunite and submetallic to dull on Romanèchite.
How to tell apart: Pyrolusite is the harder of the two (Mohs 6-6.5 vs. 3-4); streak differs — Janggunite leaves dark brown, Pyrolusite leaves black; luster reads submetallic on Janggunite and metallic on Pyrolusite.
Often found alongside janggunite
Minerals reported to co-occur with janggunite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn²⁺Mn³⁺₃O₆(OH)₂
- Mohs hardness
- 3-4
- Density
- 4.1 g/cm³
- Colors
- Streak
- Dark Brown
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, Radiating Aggregates, Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Manganese-rich Hydrothermal Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find janggunite
Classic worldwide localities
- Janggun Mine, South Korea
- Minas Gerais, Brazil
- Hokkaido, Japan
Field-hunting tip
Look in manganese-rich hydrothermal deposits country — that is the host setting where janggunite typically forms. If you start seeing rhodochrosite, manganite, hausmannite in float, you are in the right ground. Field specimens usually show a fibrous, radiating aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find janggunite on the map
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