Kayrobertsonite is a rare manganese zinc phosphate mineral discovered in granite pegmatite environments. It typically forms as small, snow-white tabular crystals and is primarily sought by advanced mineral collectors specializing in phosphate species.
Is this kayrobertsonite?
4-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 kayrobertsonite with a known reference. Kayrobertsonite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: silky.
- 3Match the color rangeCompare against the expected color range: snow-white.
- 4Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals.
Often confused with
Kayrobertsonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Fairfieldite is the harder of the two (Mohs 3.5 vs. ~2); luster reads silky on Kayrobertsonite and pearly to subadamantine, vitreous on the {001} cleavage on Fairfieldite.
How to tell apart: Brianite is the harder of the two (Mohs 4.5 vs. ~2); luster reads silky on Kayrobertsonite and vitreous on Brianite.
Often found alongside kayrobertsonite
Minerals reported to co-occur with kayrobertsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MnAl₂(PO₄)₂(OH)₂·6H₂O
- Mohs hardness
- ~2
- Density
- 2.29 g/cm³
- Colors
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage hydrothermal mineral in pegmatite as part of a complex suite of Al-rich secondary phosphates
Where rockhounds find kayrobertsonite
Classic worldwide localities
- Hagendorf Süd pegmatite, Hagendorf, Oberpfalz, Bavaria, Germany and the Foote Lithium Company mine, Kings Mountain district, Cleveland County, North Carolina, USA
Field-hunting tip
Where it forms: A late-stage hydrothermal mineral in pegmatite as part of a complex suite of Al-rich secondary phosphates. If you start seeing zwieselite-triplite, fluorapatite, nordgauite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kayrobertsonite?+
Where is kayrobertsonite found?+
What rocks look like kayrobertsonite?+
What minerals are found with kayrobertsonite?+
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Find kayrobertsonite on the map
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