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.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareJahnsite Group family

Jahnsite-(NaMnMg)

Hardness: 4
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this jahnsite-(namnmg)?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try 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.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Jahnsite-(NaMnMg) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Jahnsite-(NaMnMg) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, brown, orange-brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular to prismatic crystals, often as small crusts or aggregates.

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: NaMnMg₂Fe³⁺₂(PO₄)₄(OH)₂·8H₂O
Mohs hardness: 4
Density: 2.7-2.9 g/cm³
Colors: Yellow Brown Orange-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular to Prismatic Crystals, Often as Small Crusts or Aggregates
Cleavage: None Reported
Rarity: Rare
Uses: Collector
Host rock: Phosphate-rich Granite Pegmatites
Typical price: $50-300 per micro-mount or small specimen

Where rockhounds find jahnsite-(namnmg)

Classic worldwide localities

Tip Top Mine, South Dakota, USA
Palermo No. 1 Mine, New Hampshire, USA
Bull Moose Mine, South Dakota, USA

Field-hunting tip

Look in phosphate-rich granite pegmatites country — that is the host setting where jahnsite-(namnmg) typically forms. If you start seeing triphylite, apatite, rockbridgeite in float, you are in the right ground. Field specimens usually show a tabular to prismatic crystals, often as small crusts or aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify jahnsite-(namnmg)?+

Mohs hardness is 4. It typically shows a vitreous luster. The streak is white. Common colors include yellow, brown, orange-brown.

Where is jahnsite-(namnmg) found?+

Notable localities include Tip Top Mine, South Dakota, USA; Palermo No. 1 Mine, New Hampshire, USA; Bull Moose Mine, South Dakota, USA.

How much is jahnsite-(namnmg) worth?+

Typical asking prices fall in the range of $50-300 per micro-mount or small specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like jahnsite-(namnmg)?+

Jahnsite-(NaMnMg) is most often confused with Overite, Strunzite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with jahnsite-(namnmg)?+

Jahnsite-(NaMnMg) commonly co-occurs with Triphylite, Apatite, Rockbridgeite, Fairfieldite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does jahnsite-(namnmg) form in?+

Jahnsite-(NaMnMg) typically forms in phosphate-rich granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is jahnsite-(namnmg) used for?+

Jahnsite-(NaMnMg) is used in collector.

Find jahnsite-(namnmg) on the map

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