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 — that is 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.
