Ferristrunzite is a rare hydrated iron phosphate mineral that typically forms as delicate, radiating clusters of acicular crystals in altered pegmatite deposits. Collectors usually search for these vibrant yellow to amber tufts under magnification, as they are rarely large enough for hand-specimen display.
Is this ferristrunzite?
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 ferristrunzite with a known reference. Ferristrunzite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ferristrunzite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Ferristrunzite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brownish-yellow, amber.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular or prismatic crystals, often as radial sprays or matted aggregates.
Often confused with
Ferristrunzite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ferristrunzite
Minerals reported to co-occur with ferristrunzite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺Fe³⁺₂(PO₄)₂(OH)₃·6H₂O
- Mohs hardness
- 3.5
- Density
- 2.7 g/cm³
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Acicular or Prismatic Crystals, Often as Radial Sprays or Matted Aggregates
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Phosphate-rich Granite Pegmatites
- Typical price
- $20-150 for micromounts or small cabinet specimens
Where rockhounds find ferristrunzite
Classic worldwide localities
- Hagendorf-Sud Pegmatite, Germany
- Tip Top Mine, South Dakota, USA
- Mangualde, Portugal
- Llallagua, Bolivia
Field-hunting tip
Look in phosphate-rich granite pegmatites country — that is the host setting where ferristrunzite typically forms. If you start seeing rockbridgeite, triphylite, vivianite in float, you are in the right ground. Field specimens usually show a acicular or prismatic crystals, often as radial sprays or matted aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferristrunzite?+
Where is ferristrunzite found?+
How much is ferristrunzite worth?+
What rocks look like ferristrunzite?+
What minerals are found with ferristrunzite?+
What kind of rock does ferristrunzite form in?+
What is ferristrunzite used for?+
Find ferristrunzite on the map
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