Phosphoferrite is a rare secondary phosphate mineral typically found in phosphate-rich granite pegmatites. It is often identified by its pale, often bluish-green prismatic crystals or crystalline crusts formed by the alteration of triphylite.
Is this phosphoferrite?
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 phosphoferrite with a known reference. Phosphoferrite sits at Mohs 4-4.5, 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 subresinous.
- 4Match the color rangeCompare against the expected color range: colorless, light green, dark reddish brown, reddish brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: octahedral crystals.
Often confused with
Phosphoferrite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside phosphoferrite
Minerals reported to co-occur with phosphoferrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺₃(PO₄)₂·3H₂O
- Mohs hardness
- 4-4.5
- Density
- 3.10-3.29 g/cm³
- Streak
- White
- Luster
- Vitreous to subresinous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Octahedral crystals
- Cleavage
- On {010}, poor
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- An alteration product of triphylite in zoned complex granite pegmatites
Where rockhounds find phosphoferrite
Classic worldwide localities
- Palermo #1 mine, near North Groton, Grafton Co., New Hampshire, USA
- Dan Patch mine, 1.5 km west of Keystone, Pennington Co., and the Bull Moose and Tip Top mines, near Custer, Custer Co., South Dakota, USA
- Hagendorf, Bavaria, Germany
- Mangualde pegmatite, near Mesquitela, Portugal
- Enio pegmatite mine, northeast of Galileia, Minas Gerais, Brazil
- EI Criollo pegmatite, Cerro Blanco, Tanti district, 45 km west of Cordoba, Cordoba Province, Argentina
Field-hunting tip
Where it forms: An alteration product of triphylite in zoned complex granite pegmatites. If you start seeing ludlamite, vivianite, hureaulite in float, you are in the right ground. Typical habit: octahedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify phosphoferrite?+
Where is phosphoferrite found?+
What rocks look like phosphoferrite?+
What minerals are found with phosphoferrite?+
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What is phosphoferrite used for?+
Find phosphoferrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
