Cowlesite is a rare calcium-rich zeolite mineral often found as tiny, white, platy or lath-like crystals in basaltic cavities. Collectors look for its distinctive radiating sprays often associated with other zeolites like thomsonite and mesolite.
Is this cowlesite?
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 cowlesite with a known reference. Cowlesite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cowlesite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cowlesite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, lath-like aggregates, radiating sprays.
Often confused with
Cowlesite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside cowlesite
Minerals reported to co-occur with cowlesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₂Si₃O₁₀·6H₂O
- Mohs hardness
- 3
- Density
- 2.16 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Lath-like Aggregates, Radiating Sprays
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Basaltic Volcanic Rocks, Vugs and Cavities
- Typical price
- $20-150 per specimen
Where rockhounds find cowlesite
Classic worldwide localities
- Goblin Knob, Oregon, USA
- Juntura, Oregon, USA
- Bombay, India
- Iceland
- Scotland
Field-hunting tip
Look in basaltic volcanic rocks, vugs and cavities country — that is the host setting where cowlesite typically forms. If you start seeing analcime, chabazite, mesolite in float, you are in the right ground. Field specimens usually show a platy crystals, lath-like aggregates, radiating sprays habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cowlesite?+
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How much is cowlesite worth?+
What rocks look like cowlesite?+
What minerals are found with cowlesite?+
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Find cowlesite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
