Mordenite is a common zeolite mineral typically found in volcanic rocks as delicate, fibrous, or radiating needle-like crystal clusters. Collectors should look for its distinctive cotton-like or tufted appearances within basalt vesicles often associated with other zeolites.
Is this mordenite?
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 mordenite with a known reference. Mordenite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Mordenite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Mordenite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellow, pink, red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, acicular, radiating, or compact masses.
Often confused with
Mordenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Natrolite is the harder of the two (Mohs 5-5.5 vs. 3-4).
How to tell apart: Mesolite is the harder of the two (Mohs 5 vs. 3-4).
How to tell apart: Scolecite is the harder of the two (Mohs 5-5.5 vs. 3-4).
Often found alongside mordenite
Minerals reported to co-occur with mordenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na₂,Ca,K₂)₄(Al₈Si₄₀O₉₆)·28H₂O
- Mohs hardness
- 3-4
- Density
- 2.12-2.15 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, Acicular, Radiating, Or Compact Masses
- Cleavage
- Perfect On {100}
- Rarity
- Common
- Uses
- Collector, Industrial, Adsorbent
- Host rock
- Volcanic Cavities and Vesicles in Basalt or Rhyolite
- Typical price
- $10-60 for small specimens
Where rockhounds find mordenite
1 mapped spotsClassic worldwide localities
- Nova Scotia, Canada
- Oregon, USA
- Iceland
- Italy
- India
Field-hunting tip
Look in volcanic cavities and vesicles in basalt or rhyolite country, the host setting where mordenite typically forms. If you start seeing quartz, calcite, heulandite in float, you are in the right ground. Field specimens usually show a fibrous, acicular, radiating, or compact masses habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Colorado. Start trip planning there.
Common questions
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Find mordenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
