Plombièrite is a rare calcium silicate hydrate typically found as a result of hydrothermal activity, often in association with hot springs or as a secondary mineral in carbonate rocks. Collectors should look for delicate, white, platy or fibrous aggregates in the cavities of altered limestone.
Is this plombièrite?
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 plombièrite with a known reference. Plombièrite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Plombièrite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Plombièrite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, radial aggregates, fibrous masses.
Often confused with
Plombièrite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside plombièrite
Minerals reported to co-occur with plombièrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅Si₆O₁₈H₂·8H₂O
- Mohs hardness
- 2
- Density
- 2.1-2.2 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Radial Aggregates, Fibrous Masses
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Alteration Zones in Limestone
- Typical price
- $20-100 for small micro-mounts
Where rockhounds find plombièrite
Classic worldwide localities
- Plombières-les-Bains, France
- Santa Luce, Italy
- La Valentine, France
Field-hunting tip
Look in hydrothermal alteration zones in limestone country — that is the host setting where plombièrite typically forms. If you start seeing calcite, apophyllite, zeolites in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates, fibrous masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify plombièrite?+
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How much is plombièrite worth?+
What rocks look like plombièrite?+
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Find plombièrite on the map
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