Putnisite is a remarkably rare and chemically unique mineral discovered in Western Australia. It typically appears as small, vibrant pink to violet pseudocubic crystals on a white matrix, often found in association with other strontium-bearing minerals.
Is this putnisite?
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 putnisite with a known reference. Putnisite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Putnisite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Putnisite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: pink, violet, purple, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: pseudocubic crystals.
Often confused with
Putnisite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Strontianite is the harder of the two (Mohs 3.5 vs. 1.5-2); luster reads pearly on Putnisite and vitreous on Strontianite.
How to tell apart: Ankerite is the harder of the two (Mohs 3.5-4 vs. 1.5-2); luster reads pearly on Putnisite and vitreous on Ankerite.
Often found alongside putnisite
Minerals reported to co-occur with putnisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SrCa₄Cr⁸⁺₈(CO₃)₈SO₄(OH)₁₆·25H₂O
- Mohs hardness
- 1.5-2
- Density
- 2.36 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Pseudocubic Crystals
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Volcanic Rocks
- Typical price
- $100-500+ per specimen
Where rockhounds find putnisite
Classic worldwide localities
- Polar Bear Peninsula, Western Australia
Field-hunting tip
Look in sedimentary volcanic rocks country — that is the host setting where putnisite typically forms. If you start seeing quartz, baryte, strontianite in float, you are in the right ground. Field specimens usually show a pseudocubic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find putnisite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
