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 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Phosphofibrite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Phosphofibrite typically shows a silky luster.
- 4Match the color rangeCompare against the expected color range: green, yellowish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous aggregates, radial tufts.
Often confused with
Phosphofibrite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Phosphofibrite leaves white, Veszelyite leaves light green; luster reads silky on Phosphofibrite and vitreous on Veszelyite.
How to tell apart: Libethenite is the harder of the two (Mohs 4 vs. 3); streak differs — Phosphofibrite leaves white, Libethenite leaves pale green; luster reads silky on Phosphofibrite and vitreous on Libethenite.
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
- KCuFe³⁺₁₅(PO₄)₁₂(OH)₁₇·8H₂O
- Mohs hardness
- 3
- Density
- 3.37 g/cm³
- Colors
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous Aggregates, Radial Tufts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen
Where rockhounds find phosphofibrite
Classic worldwide localities
- Grube Clara, Germany
- Hagendorf, Germany
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where phosphofibrite typically forms. If you start seeing barite, quartz, goethite in float, you are in the right ground. Field specimens usually show a fibrous aggregates, radial tufts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find phosphofibrite on the map
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