Jahnsite-(MnMnFe) is a rare secondary phosphate mineral typically found in complex granite pegmatites. Collectors should look for small, sharp, yellow to brownish-orange crystals perched in vugs alongside other rare phosphate minerals.
Is this jahnsite-(mnmnfe)?
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-(mnmnfe) with a known reference. Jahnsite-(MnMnFe) sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Jahnsite-(MnMnFe) leaves a yellowish-white streak.
- 3Read the lusterHold the specimen under a strong light. Jahnsite-(MnMnFe) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-brown, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular to prismatic crystals, often as crusts or crystalline aggregates.
Often confused with
Jahnsite-(MnMnFe) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Jahnsite-(MnMnFe) leaves yellowish-white, Strengite leaves white.
How to tell apart: Streak differs — Jahnsite-(MnMnFe) leaves yellowish-white, Rockbridgeite leaves greenish-brown.
How to tell apart: Streak differs — Jahnsite-(MnMnFe) leaves yellowish-white, Phosphosiderite leaves white.
Often found alongside jahnsite-(mnmnfe)
Minerals reported to co-occur with jahnsite-(mnmnfe). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMn²⁺Mg₂Fe³⁺₂(PO₄)₄(OH)₂·8H₂O
- Mohs hardness
- 3-4
- Density
- 2.80-2.90 g/cm³
- Streak
- Yellowish-white
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular to Prismatic Crystals, Often as Crusts or Crystalline Aggregates
- Cleavage
- Poor On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Phosphate-rich Pegmatites
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find jahnsite-(mnmnfe)
Classic worldwide localities
- Tip Top mine, South Dakota, USA
- Big Chief mine, South Dakota, USA
- Hagendorf, Bavaria, Germany
- Mangualde, Viseu, Portugal
Field-hunting tip
Look in phosphate-rich pegmatites country — that is the host setting where jahnsite-(mnmnfe) typically forms. If you start seeing rockbridgeite, leucophosphite, hureaulite in float, you are in the right ground. Field specimens usually show a tabular to prismatic crystals, often as crusts or crystalline aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jahnsite-(mnmnfe)?+
Where is jahnsite-(mnmnfe) found?+
How much is jahnsite-(mnmnfe) worth?+
What rocks look like jahnsite-(mnmnfe)?+
What minerals are found with jahnsite-(mnmnfe)?+
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Find jahnsite-(mnmnfe) on the map
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