Hopeite is a rare hydrated zinc phosphate typically found in the oxidized zones of zinc-rich ore deposits. Collectors look for its characteristic orthorhombic prismatic crystals which often form elegant, colorless to pale yellow sprays on a matrix of smithsonite.
Is this hopeite?
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 hopeite with a known reference. Hopeite 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, pearly on {010} cleavages.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray white, yellow, light yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: encrustations, prismatic, reniform.
Often confused with
Hopeite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hopeite
Minerals reported to co-occur with hopeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Zn₃(PO₄)₂·4H₂O
- Mohs hardness
- 3.5
- Density
- 3.05-3.065 g/cm³
- Streak
- White
- Luster
- Vitreous, pearly on {010} cleavages
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Encrustations, prismatic, reniform
- Cleavage
- Perfect on {010}; good on {100}; poor on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare, late-stage mineral in some hydrothermal zinc deposits and complex granite pegmatites; incrusting bone breccia in a limestone cave
Where rockhounds find hopeite
Classic worldwide localities
- Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
- Palermo #1 mine, near North Groton, Grafton Co., New Hampshire, USA
- Iron Cap Pb–Zn mine, near Aravaipa, Graham Co., Arizona, USA
- Found at Vieille Montagne (Altenberg), Moresnet district, Belgium
- Bad Ems, Rhineland-Palatinate, Germany
- Hagendorf, Bavaria, Germany
Field-hunting tip
Where it forms: A rare, late-stage mineral in some hydrothermal zinc deposits and complex granite pegmatites; incrusting bone breccia in a limestone cave. If you start seeing tarbuttite, hemimorphite, spencerite in float, you are in the right ground. Typical habit: encrustations, prismatic, reniform. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hopeite?+
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Find hopeite on the map
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