Jahnsite-(NaMnMg) is a rare phosphate mineral typically found as secondary crusts or small crystals in the alteration zones of granite pegmatites. Collectors often find these alongside other phosphate species where primary minerals like triphylite have undergone chemical weathering.
Is this jahnsite-(namnmg)?
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 jahnsite-(namnmg) with a known reference. Jahnsite-(NaMnMg) 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. Streak: very pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, striated.
Often confused with
Jahnsite-(NaMnMg) vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside jahnsite-(namnmg)
Minerals reported to co-occur with jahnsite-(namnmg). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,Ca)(Mn,Fe)(Mg,Fe)₂Fe₂(PO₄)₄(OH)₂(H₂O)₈
- Mohs hardness
- ~4
- Density
- 2.68-2.69 g/cm³
- Colors
- Streak
- Very pale yellow
- Luster
- Vitreous
- Transparency
- Translucent to transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, striated
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A low temperature, secondary mineral formed by alteration of primary phosphates in zoned granitic pegmatite
Where rockhounds find jahnsite-(namnmg)
Classic worldwide localities
- Tip Top pegmatite, South Dakota, USA
- Sapucaia pegmatite, 12 km north northeast of Galiléia, Conselheiro Pena district, Minas Gerais, Brazil and the White Rock No. 2 quarry, Bimbowrie Conservation Park, ~22 km north of Olary, South Australia, Australia
Field-hunting tip
Where it forms: A low temperature, secondary mineral formed by alteration of primary phosphates in zoned granitic pegmatite. If you start seeing frondelite, albite, meurigite-k in float, you are in the right ground. Typical habit: prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jahnsite-(namnmg)?+
Where is jahnsite-(namnmg) found?+
What rocks look like jahnsite-(namnmg)?+
What minerals are found with jahnsite-(namnmg)?+
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Find jahnsite-(namnmg) on the map
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