Paulkerrite is a rare phosphate mineral typically found as delicate, pale yellow to brownish-tan platy crystals. It most commonly occurs within phosphate-rich zones of granitic pegmatites, often forming radial or sheaf-like aggregates. Due to its scarcity and fragile habit, it is primarily a target for specialized mineral collectors.
Is this paulkerrite?
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 paulkerrite with a known reference. Paulkerrite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Paulkerrite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Paulkerrite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-brown, tan.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, radial aggregates.
Often confused with
Paulkerrite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside paulkerrite
Minerals reported to co-occur with paulkerrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KMgAl₂(PO₄)₂(OH)₂·8H₂O
- Mohs hardness
- 3-4
- Density
- 2.81 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find paulkerrite
Classic worldwide localities
- Tip Top Mine, South Dakota, USA
- Bull Moose Mine, South Dakota, USA
Field-hunting tip
Look in granite pegmatites country, the host setting where paulkerrite typically forms. If you start seeing quartz, muscovite, albite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find paulkerrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
