Nagashimalite is an extremely rare barium vanadium silicate mineral typically found in metamorphosed manganese deposits in Japan. It usually occurs as small, dark brown to black tabular crystals or granular aggregates, often requiring microscopic examination for positive identification.
Is this nagashimalite?
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 nagashimalite with a known reference. Nagashimalite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Nagashimalite leaves a yellowish brown streak.
- 3Read the lusterHold the specimen under a strong light. Nagashimalite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, aggregates.
Often confused with
Nagashimalite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside nagashimalite
Minerals reported to co-occur with nagashimalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ba₄(V³⁺,Ti)₄Si₈B₂O₂₇(O,OH)₂Cl
- Mohs hardness
- 4
- Density
- 3.8 g/cm³
- Colors
- Streak
- Yellowish Brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Aggregates
- Cleavage
- Distinct On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Bedded Manganese Ore Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find nagashimalite
Classic worldwide localities
- Nagashiba, Yamaguchi Prefecture, Japan
- Hojun mine, Gunma Prefecture, Japan
Field-hunting tip
Look in metamorphosed bedded manganese ore deposits country — that is the host setting where nagashimalite typically forms. If you start seeing quartz, baryte, kainosite-(y) in float, you are in the right ground. Field specimens usually show a tabular crystals, aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find nagashimalite on the map
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