Kingsmountite is a rare phosphate mineral primarily known from the iron-rich sedimentary deposits of the Yukon. It typically forms delicate, needle-like acicular crystals or radiating sprays that are highly sought after by mineral collectors for their aesthetic crystallization.
Is this kingsmountite?
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 kingsmountite with a known reference. Kingsmountite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to fibrous.
- 4Match the color rangeCompare against the expected color range: light brown, pearl white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed, radial, spherical.
Often confused with
Kingsmountite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Vauxite is the harder of the two (Mohs 3.5 vs. ~2.5); luster reads pearly to fibrous on Kingsmountite and vitreous on Vauxite.
How to tell apart: Luster reads pearly to fibrous on Kingsmountite and vitreous, pearly on cleavages on Paravauxite.
Often found alongside kingsmountite
Minerals reported to co-occur with kingsmountite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃MnFeAl₄(PO₄)₆(OH)₄·12H₂O
- Mohs hardness
- ~2.5
- Density
- 2.51 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly to fibrous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed, radial, spherical
- Cleavage
- Perfect in one direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed from alteration of primary phosphates by descending oxidizing ground water in complex granite pegmatites
Where rockhounds find kingsmountite
Classic worldwide localities
- Foote mine, near Kings Mountain, Cleveland Co., North Carolina, USA
- Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
- Twin Creeks mine, Potosi district, Humboldt Co., Nevada, USA
- Mt. Vasin-Myl’k, Voron’i massif, Kola Peninsula, Russia
- Bendada pegmatite, near Guarda, Portugal
- Silbergrube quarry, near Waidhaus, and at Hagendorf, Bavaria, Germany
Field-hunting tip
Where it forms: A secondary mineral formed from alteration of primary phosphates by descending oxidizing ground water in complex granite pegmatites. If you start seeing mitridatite, birnessite, whitlockite in float, you are in the right ground. Typical habit: bladed, radial, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kingsmountite?+
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What rocks look like kingsmountite?+
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Find kingsmountite on the map
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