Phosphofibrite is a rare phosphate mineral characterized by its delicate, fibrous, and radial habit often occurring in tufts. It is primarily identified by its distinct green color and association with secondary mineral deposits in hydrothermal veins, typically requiring microscopic analysis for definitive confirmation.
Is this phosphofibrite?
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 phosphofibrite with a known reference. Phosphofibrite 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.
- 4Match the color rangeCompare against the expected color range: yellow, yellow green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous aggregates, radial tufts.
Often confused with
Phosphofibrite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside phosphofibrite
Minerals reported to co-occur with phosphofibrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (H₂O,K)₃.₅Fe₈(PO₄)₆(OH)₇(H₂O)₅
- Mohs hardness
- ~4
- Density
- 2.90 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous aggregates, radial tufts
- Cleavage
- One, nearly perfect, pinacoidal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a hydrothermal polymetallic barite–fluorite deposit
Where rockhounds find phosphofibrite
Classic worldwide localities
- Clara mine, near Oberwolfach, Black Forest, Germany
Field-hunting tip
Where it forms: In a hydrothermal polymetallic barite–fluorite deposit. If you start seeing beraunite, strengite, barian pharmacosiderite in float, you are in the right ground. Typical habit: fibrous aggregates, radial tufts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify phosphofibrite?+
Where is phosphofibrite found?+
What rocks look like phosphofibrite?+
What minerals are found with phosphofibrite?+
What kind of rock does phosphofibrite form in?+
What is phosphofibrite used for?+
Find phosphofibrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
