Strengite is an attractive iron phosphate mineral often sought by collectors for its vibrant violet to raspberry-red colors. It typically forms as radiating spherical, botryoidal, or drusy aggregates, and is commonly found in the oxidized zones of iron-rich mineral deposits.
Is this strengite?
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 strengite with a known reference. Strengite sits at Mohs 3.5, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: red, colorless, pale violet, deep violet, carmine red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: botryoidal, radial, spherical.
Often confused with
Strengite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside strengite
Minerals reported to co-occur with strengite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FePO₄·2H₂O
- Mohs hardness
- 3.5
- Density
- 2.84-2.87 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Botryoidal, radial, spherical
- Cleavage
- On {010}, good; on {001}, poor
- Rarity
- Uncommon
- Uses
- Collector, Ornamental
- Host rock
- A late secondary mineral in complex granite pegmatites; in “limonite” iron ores and gossans; with magnetite iron ores; rarely a cave mineral
Where rockhounds find strengite
Classic worldwide localities
- Palermo #1 and Fletcher mines, near North Groton, Grafton Co., New Hampshire, USA
- Midvale, Rockbridge Co., Virginia, USA
- Indian Mountain, Cherokee Co., Alabama, USA
- Three Oak Gap and the Coon Creek mine, Polk Co., Arkansas, USA
- Eleonore and Rotläufchen iron mines, near Giessen, Hesse, Germany
- Hagendorf, and on the Kreuzberg, Pleystein, Bavaria, Germany
Field-hunting tip
Where it forms: A late secondary mineral in complex granite pegmatites; in “limonite” iron ores and gossans; with magnetite iron ores; rarely a cave mineral. If you start seeing beraunite, huréaulite, dufrénite in float, you are in the right ground. Typical habit: botryoidal, radial, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
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Find strengite on the map
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