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 — 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 — that is 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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