Gatumbaite is a rare phosphate mineral typically found as delicate, radiating clusters of acicular crystals within phosphate-rich pegmatites. It was first identified in the Gatumba pegmatite field of Rwanda and remains a highly sought-after specimen for advanced phosphate mineral collectors.

Hardness

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrare

Gatumbaite

Hardness: <5
Luster: Pearly
Streak: White
Transparency: Translucent

Is this gatumbaite?

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 gatumbaite with a known reference. Gatumbaite sits at Mohs <5, 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: pearly.
4
Match the color range
Compare against the expected color range: white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: rosette, scaly, wheat sheaf.

Often confused with

Gatumbaite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Crandallite

Mohs 5

How to tell apart: Luster reads pearly on Gatumbaite and vitreous, dull to chalky when massive on Crandallite.

How to tell apart: Luster reads pearly on Gatumbaite and vitreous to waxy on Variscite.

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Often found alongside gatumbaite

Minerals reported to co-occur with gatumbaite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: CaAl₂(PO₄)₂(OH)₂·H₂O
Mohs hardness: <5
Density: 2.92 g/cm³
Colors: White
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Rosette, scaly, wheat sheaf
Cleavage: Good
Rarity: Rare
Uses: Collector
Host rock: From the phosphate assemblage in a complex granite pegmatite (Buranga pegmatite, Rwanda; Hålsjöberg, Sweden.); in andesites altered hydrothermally through hydrogen metasomatism (Mt. Perry, Australia)

Where rockhounds find gatumbaite

Classic worldwide localities

Buranga pegmatite, near Gatumba, Rwanda
Mt. Perry, 75 km southwest of Bundaberg, Queensland, Australia
Hålsjöberg, Värmland, Sweden

Field-hunting tip

Where it forms: From the phosphate assemblage in a complex granite pegmatite (Buranga pegmatite, Rwanda; Hålsjöberg, Sweden.); in andesites altered hydrothermally through hydrogen metasomatism (Mt. Perry, Australia). If you start seeing trolleite, scorzalite, apatite in float, you are in the right ground. Typical habit: rosette, scaly, wheat sheaf. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gatumbaite?+

Mohs hardness is <5. Luster: pearly. The streak is white. Common colors include white.

Where is gatumbaite found?+

Notable localities include Buranga pegmatite, near Gatumba, Rwanda; Mt. Perry, 75 km southwest of Bundaberg, Queensland, Australia; Hålsjöberg, Värmland, Sweden.

What rocks look like gatumbaite?+

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

What minerals are found with gatumbaite?+

Gatumbaite commonly co-occurs with Trolleite, Scorzalite, Apatite, Bjarebyite, Burangaite, Augelite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gatumbaite form in?+

Where it forms: From the phosphate assemblage in a complex granite pegmatite (Buranga pegmatite, Rwanda; Hålsjöberg, Sweden.); in andesites altered hydrothermally through hydrogen metasomatism (Mt. Perry, Australia). Working float back to the host body is the standard way to chase a fresh occurrence.

What is gatumbaite used for?+

Gatumbaite is used in collector.

Find gatumbaite on the map

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