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.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrarePaulkerrite Group family

Paulkerrite

Hardness: ~3
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this paulkerrite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch paulkerrite with a known reference. Paulkerrite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, yellow brown, light yellow brown.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: euhedral crystals.

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: [(H₂O)K]Mg₂(Fe³⁺₂Ti)(PO₄)₄(OF)(H₂O)₁₀·4H₂O
Mohs hardness: ~3
Density: 2.36 g/cm³
Colors: Colorless Yellow brownLight yellow brown
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Euhedral crystals
Cleavage: On {100}, perfect
Rarity: Rare
Uses: Collector
Host rock: An alteration product of triplite in complex zoned granite pegmatites

Where rockhounds find paulkerrite

Classic worldwide localities

Bendada pegmatite, near Guarda, Portugal

Field-hunting tip

Where it forms: An alteration product of triplite in complex zoned granite pegmatites. If you start seeing triplite, bermanite, phosphosiderite in float, you are in the right ground. Typical habit: euhedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify paulkerrite?+

Mohs hardness is ~3. Luster: vitreous. The streak is white. Common colors include colorless, yellow brown, light yellow brown.

Where is paulkerrite found?+

Notable localities include Bendada pegmatite, near Guarda, Portugal.

What rocks look like paulkerrite?+

Paulkerrite is most often confused with Vauxite, Paravauxite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with paulkerrite?+

Paulkerrite commonly co-occurs with Triplite, Bermanite, Phosphosiderite, Leucophosphite, Strengite, Switzerite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does paulkerrite form in?+

Where it forms: An alteration product of triplite in complex zoned granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is paulkerrite used for?+

Paulkerrite is used in collector.

Find paulkerrite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.