Jahnsite-(CaMnFe) is a rare secondary phosphate mineral typically found in the oxidized zones of granite pegmatites. Collectors look for its characteristic yellowish-brown tabular crystals occurring in small cavities with other phosphate minerals.
Is this jahnsite-(camnfe)?
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-(camnfe) with a known reference. Jahnsite-(CaMnFe) 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to subadamantine.
- 4Match the color rangeCompare against the expected color range: yellow, brown, purplish brown, yellow orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular to prismatic crystals, often as tiny crusts or aggregates.
Often confused with
Jahnsite-(CaMnFe) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Jahnsite-(CaMnFe) is noticeably harder (Mohs 4 vs. 3); streak differs, so Jahnsite-(CaMnFe) leaves white, Whitmoreite leaves yellow-brown.
How to tell apart: Jahnsite-(CaMnFe) is noticeably harder (Mohs 4 vs. 3).
How to tell apart: Jahnsite-(CaMnFe) is noticeably harder (Mohs 4 vs. 3).
Often found alongside jahnsite-(camnfe)
Minerals reported to co-occur with jahnsite-(camnfe). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMnFe²⁺₂(H₂O)₈Fe³⁺₂(PO₄)₄(OH)₂
- Mohs hardness
- 4
- Density
- 2.86 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to subadamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular to prismatic crystals, often as tiny crusts or aggregates
- Cleavage
- Good on {001} by analogy to jahnsite-(CaMnMg)
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- A late-stage hydrothermal decomposition product of primary phosphate minerals in complex granite pegmatites
Where rockhounds find jahnsite-(camnfe)
Classic worldwide localities
- Fletcher and Palermo # 1 mines, near North Groton, Grafton Co., New Hampshire, USA
- Dunton quarry and the Bell pit, Newry, Oxford Co., Maine, USA
- Hagendorf, Bavaria, Germany
- Sapucaia pegmatite mine, about 50 km east-southeast of Governador Valadares, Minas Gerais, Brazil
Field-hunting tip
Where it forms: A late-stage hydrothermal decomposition product of primary phosphate minerals in complex granite pegmatites. If you start seeing rockbridgeite, frondelite, bermanite in float, you are in the right ground. Typical habit: tabular to prismatic crystals, often as tiny crusts or aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jahnsite-(camnfe)?+
Where is jahnsite-(camnfe) found?+
What rocks look like jahnsite-(camnfe)?+
What minerals are found with jahnsite-(camnfe)?+
What kind of rock does jahnsite-(camnfe) form in?+
What is jahnsite-(camnfe) used for?+
Find jahnsite-(camnfe) on the map
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