Planerite is a relatively rare hydrated aluminum phosphate mineral that typically forms as botryoidal crusts or radial aggregates. Collectors often find it as a secondary mineral in phosphate-rich environments, frequently associated with variscite and wavellite. It is best identified by its distinct habit and occurrence within weathered aluminum-bearing phosphate deposits.
Is this planerite?
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 planerite with a known reference. Planerite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: blue white.
- 3Read the lusterHold the specimen under a strong light. Luster: dull, chalky to earthy.
- 4Match the color rangeCompare against the expected color range: bluish green, light blue, light green, olive green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: botryoidal, encrustations.
Often confused with
Planerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Planerite leaves blue white, Variscite leaves white; luster reads dull, chalky to earthy on Planerite and vitreous to waxy on Variscite.
How to tell apart: Streak differs, so Planerite leaves blue white, Wardite leaves white; luster reads dull, chalky to earthy on Planerite and vitreous on Wardite.
How to tell apart: Streak differs, so Planerite leaves blue white, Crandallite leaves white; luster reads dull, chalky to earthy on Planerite and vitreous, dull to chalky when massive on Crandallite.
Often found alongside planerite
Minerals reported to co-occur with planerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₆(PO₄)₂(PO₃OH)₂(OH)₈·4H₂O
- Mohs hardness
- 5
- Density
- 2.65-2.68 g/cm³
- Streak
- Blue white
- Luster
- Dull, chalky to earthy
- Transparency
- Translucent on edges
- Crystal system
- Triclinic
- Crystal habit
- Botryoidal, encrustations
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral formed in phosphate-rich aluminous deposits
Where rockhounds find planerite
Classic worldwide localities
- General Trimble’s mine, Chester Co., Pennsylvania, USA
- Mauldin Mountain quarry, near Mt. Ida, Montgomery Co., at the Coon Creek mine and Buckeye Mountain, Polk Co., and on Dug Hill, near Avant, Garland Co., Arkansas, USA
- Erin, Clay Co., Alabama, USA
- Brewer, east of Cedartown, Polk Co., Georgia, USA
- Mt. Chernovskaya, near the Chernaya River, Middle Ural Mountains, Russia
- Poniklá, Jilemnice, Czech Republic
Field-hunting tip
Where it forms: A rare secondary mineral formed in phosphate-rich aluminous deposits. If you start seeing wavellite, variscite, metavariscite in float, you are in the right ground. Typical habit: botryoidal, encrustations. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify planerite?+
Where is planerite found?+
What rocks look like planerite?+
What minerals are found with planerite?+
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What is planerite used for?+
Find planerite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
