Hedegaardite is a very rare phosphate mineral found in specific sedimentary environments where organic matter interacts with phosphate-rich groundwater. It typically forms small, prismatic yellow crystals that are highly sensitive to dehydration and light exposure, often requiring careful storage.
Is this hedegaardite?
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 hedegaardite with a known reference. Hedegaardite 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. Hedegaardite leaves a yellowish-white streak.
- 3Read the lusterHold the specimen under a strong light. Hedegaardite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brownish-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Hedegaardite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Hedegaardite is noticeably harder (Mohs 3 vs. 1.5-2); streak differs — Hedegaardite leaves yellowish-white, Vivianite leaves white to light blue.
How to tell apart: Hedegaardite is noticeably harder (Mohs 3 vs. 1.5-2); streak differs — Hedegaardite leaves yellowish-white, Metavivianite leaves greenish-white.
Often found alongside hedegaardite
Minerals reported to co-occur with hedegaardite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)Mn₂Fe₂(PO₄)₃·3H₂O
- Mohs hardness
- 3
- Density
- 2.81 g/cm³
- Colors
- Streak
- Yellowish-white
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find hedegaardite
Classic worldwide localities
- Skarlev, Denmark
Field-hunting tip
Look in sedimentary deposits country — that is the host setting where hedegaardite typically forms. If you start seeing vivianite, siderite, quartz in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find hedegaardite on the map
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