Jimboite is a rare manganese borate mineral that typically forms as small, prismatic crystals within manganese-rich contact metamorphic environments. Collectors primarily find it in specific high-grade manganese deposits, most notably in Japan where it was first discovered.
Is this jimboite?
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 jimboite with a known reference. Jimboite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: light purple brown, reddish brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals.
Often confused with
Jimboite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside jimboite
Minerals reported to co-occur with jimboite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₃(BO₃)₂
- Mohs hardness
- 5.5
- Density
- 3.98-4.02 g/cm³
- Colors
- Light purple brownReddish brown
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic crystals
- Cleavage
- On {110}, perfect; {101}, a parting
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Likely formed by metasomatic reactions between boron-bearing hydrothermal solutions and rhodochrosite in banded manganese deposits
Where rockhounds find jimboite
Classic worldwide localities
- Kaso mine, Kanuma, Tochigi Prefecture, Japan
- Rito mine, Seta, Gumma Prefecture, Japan
- Fuji mine, Fukui Prefecture, Japan
Field-hunting tip
Where it forms: Likely formed by metasomatic reactions between boron-bearing hydrothermal solutions and rhodochrosite in banded manganese deposits. If you start seeing rhodochrosite, tephroite, galaxite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jimboite?+
Where is jimboite found?+
What rocks look like jimboite?+
What minerals are found with jimboite?+
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Find jimboite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
