Penikisite is a rare barium-magnesium phosphate mineral that occurs as small, delicate crystals. It is most famously found in the phosphate-rich concretions of the Big Fish River and Rapid Creek regions in Yukon, Canada, often associated with other rare phosphate species.
Is this penikisite?
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 penikisite with a known reference. Penikisite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale green to white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue, green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy, rosette.
Often confused with
Penikisite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Wardite is the harder of the two (Mohs 5 vs. ~4); streak differs, so Penikisite leaves very pale green to white, Wardite leaves white.
How to tell apart: Streak differs, so Penikisite leaves very pale green to white, Gormanite leaves pale green.
Often found alongside penikisite
Minerals reported to co-occur with penikisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaMg₂Al₂(PO₄)₃(OH)₃
- Mohs hardness
- ~4
- Density
- 3.79 g/cm³
- Streak
- Very pale green to white
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy, rosette
- Cleavage
- On {010} and {100}, fair to good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare weathering product in fractures in sideritic iron formation
Where rockhounds find penikisite
Classic worldwide localities
- Cross-cut Creek, Big Fish River–Blow River area, and in the Hess River area, Yukon Territory, Canada
Field-hunting tip
Where it forms: A very rare weathering product in fractures in sideritic iron formation. If you start seeing kulanite, quartz, siderite in float, you are in the right ground. Typical habit: platy, rosette. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify penikisite?+
Where is penikisite found?+
What rocks look like penikisite?+
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Find penikisite on the map
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