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 4.5, 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: colorless, gray blue, light green.
- 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.
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
- 4.5
- Density
- 3.194 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral crystals, often showing complex faces
- Cleavage
- Perfect on {1012}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral, formed by late hydrothermal alteration, probably of beryl and zircon, in complex granite pegmatites
Where rockhounds find kosnarite
Classic worldwide localities
- Mt. Mica, near Paris, and in the Black Mountain quarry, near Rumford, Oxford Co., Maine, USA
- Wycheproof, Victoria, Australia
Field-hunting tip
Where it forms: A very rare mineral, formed by late hydrothermal alteration, probably of beryl and zircon, in complex granite pegmatites. If you start seeing eosphorite, fluorapatite, moraesite in float, you are in the right ground. Typical habit: rhombohedral crystals, often showing complex faces. 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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