Manganoneptunite is a rare manganese-dominant member of the neptunite group, distinguished from common neptunite by its specific chemical composition. It typically forms sharp, lustrous black prismatic crystals associated with rare-earth minerals in alkaline pegmatites, often found in complex specimens from Mont Saint-Hilaire.
Is this manganoneptunite?
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 manganoneptunite with a known reference. Manganoneptunite sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Manganoneptunite leaves a brownish red streak.
- 3Read the lusterHold the specimen under a strong light. Manganoneptunite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Manganoneptunite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside manganoneptunite
Minerals reported to co-occur with manganoneptunite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KNa₂Li(Mn,Fe)₂Ti₂Si₈O₂₄
- Mohs hardness
- 5-6
- Density
- 3.19-3.23 g/cm³
- Colors
- Streak
- Brownish Red
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Distinct On {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks and Pegmatites
- Typical price
- $50-500 per specimen
Where rockhounds find manganoneptunite
Classic worldwide localities
- Narssârssuk, Greenland
- Mont Saint-Hilaire, Canada
- Khibiny Massif, Russia
Field-hunting tip
Look in alkaline igneous rocks and pegmatites country — that is the host setting where manganoneptunite typically forms. If you start seeing eudialyte, serandite, leifite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify manganoneptunite?+
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How much is manganoneptunite worth?+
What rocks look like manganoneptunite?+
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Find manganoneptunite on the map
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