Jianshuiite is a rare manganese oxide mineral typically found in sedimentary manganese ore deposits. It is often identified as soft, earthy, or pulverulent masses that look similar to other black manganese oxides, making positive identification dependent on laboratory analysis like XRD.
Is this jianshuiite?
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 jianshuiite with a known reference. Jianshuiite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: brown, brownish black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: aggregates, granular, massive.
Often confused with
Jianshuiite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Jianshuiite leaves brown, Birnessite leaves brownish-black; luster reads metallic on Jianshuiite and dull on Birnessite.
How to tell apart: Streak differs, so Jianshuiite leaves brown, Todorokite leaves black.
How to tell apart: Psilomelane is the harder of the two (Mohs 5-6 vs. 1.5-2); streak differs, so Jianshuiite leaves brown, Psilomelane leaves brownish black; luster reads metallic on Jianshuiite and submetallic on Psilomelane.
Often found alongside jianshuiite
Minerals reported to co-occur with jianshuiite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgMn₃O₇·3H₂O
- Mohs hardness
- 1.5-2
- Density
- 3.50-3.60 g/cm³
- Colors
- Streak
- Brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Aggregates, granular, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A hypogene mineral in manganese ore (Lu Village, China); authigenic in manganese oxide concretions in siltstone (San Felipe, Mexico)
Where rockhounds find jianshuiite
Classic worldwide localities
- Lu Village, Jianshui Co., Yunnan Province, China
Field-hunting tip
Where it forms: A hypogene mineral in manganese ore (Lu Village, China); authigenic in manganese oxide concretions in siltstone (San Felipe, Mexico). If you start seeing hydrated manganese oxides, magnetite, maghemite in float, you are in the right ground. Typical habit: aggregates, granular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find jianshuiite on the map
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