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, 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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