Kosnarite is a rare zirconium phosphate mineral typically found as small, sharp rhombohedral crystals in granite pegmatites. Collectors look for its characteristic glassy luster and complex crystal habit, usually associated with other phosphate minerals in miarolitic cavities.
Is this kosnarite?
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 kosnarite with a known reference. Kosnarite 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. Kosnarite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kosnarite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellow, brownish.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rhombohedral crystals, often showing complex faces.
Often confused with
Kosnarite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Monazite is the harder of the two (Mohs 5-5.5 vs. 3.5); luster reads vitreous on Kosnarite and resinous on Monazite.
How to tell apart: Zircon is the harder of the two (Mohs 7.5 vs. 3.5); luster reads vitreous on Kosnarite and adamantine on Zircon.
Often found alongside kosnarite
Minerals reported to co-occur with kosnarite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KZr₂(PO₄)₃
- Mohs hardness
- 3.5
- Density
- 2.88 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral Crystals, Often Showing Complex Faces
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-500 depending on crystal size and clarity
Where rockhounds find kosnarite
Classic worldwide localities
- Mount Mica Quarry, Maine, USA
- Manjaka, Madagascar
- Lavra da Ilha, Brazil
Field-hunting tip
Look in granite pegmatites country — that is the host setting where kosnarite typically forms. If you start seeing quartz, albite, muscovite in float, you are in the right ground. Field specimens usually show a rhombohedral crystals, often showing complex faces habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find kosnarite on the map
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