Koninckite is a rare hydrated iron phosphate that typically forms as small radiating clusters or earthy crusts within iron-rich sedimentary deposits. It is frequently found as an alteration product in association with goethite or limonite. Collectors prize it for its delicate, needle-like formations and vibrant yellow coloration.
Is this koninckite?
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 koninckite with a known reference. Koninckite 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. Koninckite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Koninckite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-white, colorless.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: radiating aggregates, globular, crusts.
Often confused with
Koninckite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Koninckite is noticeably harder (Mohs 3.5 vs. 1.5-2); streak differs, so Koninckite leaves white, Vivianite leaves white to light blue.
How to tell apart: Luster reads vitreous on Koninckite and waxy on Variscite.
Often found alongside koninckite
Minerals reported to co-occur with koninckite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FePO₄·3H₂O
- Mohs hardness
- 3.5
- Density
- 2.44 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Radiating Aggregates, Globular, Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Iron Ore Deposits
- Typical price
- $20-100 per specimen
Where rockhounds find koninckite
Classic worldwide localities
- Visé, Belgium
- Amberg, Germany
- Iron Mountain, Missouri, USA
Field-hunting tip
Look in sedimentary iron ore deposits country, the host setting where koninckite typically forms. If you start seeing limonite, goethite, quartz in float, you are in the right ground. Field specimens usually show a radiating aggregates, globular, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find koninckite on the map
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