Whitmoreite is a rare iron phosphate mineral typically found as brown, bladed, or radial crystal clusters in oxidized phosphate zones of pegmatites. It is highly valued by advanced micromount collectors due to its distinct, well-defined crystal habit and vibrant brown color. It is primarily identified by its occurrence in specific secondary phosphate assemblages.
Is this whitmoreite?
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 whitmoreite with a known reference. Whitmoreite 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. Whitmoreite leaves a yellow-brown streak.
- 3Read the lusterHold the specimen under a strong light. Whitmoreite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, yellow-brown, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed crystals, radial aggregates, crusts.
Often confused with
Whitmoreite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Rockbridgeite is the harder of the two (Mohs 4.5 vs. 2.5); streak differs — Whitmoreite leaves yellow-brown, Rockbridgeite leaves greenish-brown.
How to tell apart: Strengite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs — Whitmoreite leaves yellow-brown, Strengite leaves white.
Often found alongside whitmoreite
Minerals reported to co-occur with whitmoreite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺Fe³⁺₂(PO₄)₂(OH)₂·4H₂O
- Mohs hardness
- 2.5
- Density
- 2.83 g/cm³
- Streak
- Yellow-brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed Crystals, Radial Aggregates, Crusts
- Cleavage
- Good On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Phosphate-rich Granite Pegmatites
- Typical price
- $20-150 for micromounts and small specimens
Where rockhounds find whitmoreite
Classic worldwide localities
- Big Chief mine, South Dakota, USA
- Palermo #1 mine, New Hampshire, USA
- Hagendorf, Germany
Field-hunting tip
Look in phosphate-rich granite pegmatites country — that is the host setting where whitmoreite typically forms. If you start seeing siderite, triphylite, rockbridgeite in float, you are in the right ground. Field specimens usually show a bladed crystals, radial aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find whitmoreite on the map
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