Zwieselite is a relatively rare phosphate mineral typically found as massive or granular aggregates within phosphate-rich pegmatites. It is visually similar to triplite but distinguished by its distinct chemical composition; it is primarily found in granite pegmatites associated with other phosphate minerals.
Is this zwieselite?
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 zwieselite with a known reference. Zwieselite 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. Zwieselite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Zwieselite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, clove-brown, yellow-brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, granular, rarely as distinct crystals.
Often confused with
Zwieselite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside zwieselite
Minerals reported to co-occur with zwieselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe²⁺₂PO₄F
- Mohs hardness
- 5
- Density
- 3.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Granular, Rarely as Distinct Crystals
- Cleavage
- Distinct On {010}
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Granite Pegmatites
- Typical price
- $20-150 per specimen depending on size and quality
Where rockhounds find zwieselite
Classic worldwide localities
- Zwiesel, Bavaria, Germany
- Newry, Maine, USA
- Hagendorf, Bavaria, Germany
- Linopolis, Minas Gerais, Brazil
Field-hunting tip
Look in granite pegmatites country, the host setting where zwieselite typically forms. If you start seeing triplite, apatite, beryl in float, you are in the right ground. Field specimens usually show a massive, granular, rarely as distinct crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify zwieselite?+
Where is zwieselite found?+
How much is zwieselite worth?+
What rocks look like zwieselite?+
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Find zwieselite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
