Jahnsite-(CaFeMg) is a rare phosphate mineral typically found as small, yellow to brown tabular crystals within phosphate-rich zones of granite pegmatites. Collectors look for them in the vugs of altered triphylite or other primary phosphates, often requiring magnification for accurate identification.
Is this jahnsite-(cafemg)?
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-(cafemg) with a known reference. Jahnsite-(CaFeMg) 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. Jahnsite-(CaFeMg) leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Jahnsite-(CaFeMg) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, orange-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, sometimes in radiating aggregates.
Often found alongside jahnsite-(cafemg)
Minerals reported to co-occur with jahnsite-(cafemg). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaFe²⁺Mg₂Fe³⁺₂(PO₄)₄(OH)₂·8H₂O
- Mohs hardness
- 4
- Density
- 2.7 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Sometimes in Radiating Aggregates
- Cleavage
- Poor On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find jahnsite-(cafemg)
Classic worldwide localities
- Tip Top Mine, South Dakota, USA
- Palermo No. 1 Mine, New Hampshire, USA
- Hagendorf-Pleystein, Bavaria, Germany
Field-hunting tip
Look in granite pegmatites country — that is the host setting where jahnsite-(cafemg) typically forms. If you start seeing triphylite, rockbridgeite, apatite in float, you are in the right ground. Field specimens usually show a tabular crystals, sometimes in radiating aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify jahnsite-(cafemg)?+
Where is jahnsite-(cafemg) found?+
How much is jahnsite-(cafemg) worth?+
What minerals are found with jahnsite-(cafemg)?+
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Find jahnsite-(cafemg) on the map
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