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
Classic worldwide localities
- Nova Scotia, Canada
- Oregon, USA
- Iceland
- Italy
- India
Field-hunting tip
Look in volcanic cavities and vesicles in basalt or rhyolite country — that is 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.
Common questions
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Find mordenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
