Pollucite is a rare zeolite mineral that serves as the primary ore for the element cesium. It most commonly occurs in highly evolved granite pegmatites, often forming complex trapezohedral crystals or appearing as massive, quartz-like white clumps embedded in a matrix of lepidolite and spodumene.
Is this pollucite?
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 pollucite with a known reference. Pollucite sits at Mohs 6.5-7, 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; greasy to dull on the exterior.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray, pale pink, blue.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive.
Often confused with
Pollucite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside pollucite
Minerals reported to co-occur with pollucite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cs(Si₂Al)O₆·nH₂O
- Mohs hardness
- 6.5-7
- Density
- 2.68-3.03 g/cm³
- Streak
- White
- Luster
- Vitreous; greasy to dull on the exterior
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
- Crystal habit
- Massive
- Cleavage
- In traces
- Fluorescence
- Cream white blue green under SW UV; weak orange under LW UV
- Rarity
- Uncommon
- Uses
- Collector, Cesium ore
- Host rock
- In lithium-rich granite pegmatites; may be in kiloton amounts
Where rockhounds find pollucite
1 mapped spotsClassic worldwide localities
- A number of localities in Oxford Co., Maine, USA
- Portland and Haddam, Middlesex Co., Connecticut, USA
- Tin Mountain mine, near Custer, Custer Co., South Dakota, USA
- Pala and Mesa Grande districts, San Diego Co., California, USA
- San Piero in Campo, Elba, Italy
- Varuträsk pegmatite, 15 km northwest of Skellefteå, Västerbotten, Sweden
Field-hunting tip
Where it forms: In lithium-rich granite pegmatites; may be in kiloton amounts. If you start seeing quartz, spodumene, petalite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Connecticut. Start trip planning there.
Common questions
How do you identify pollucite?+
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Can I find pollucite in the United States?+
What rocks look like pollucite?+
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Find pollucite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
