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, 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?+
Where is cowlesite found?+
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.
