Laumontite is a common zeolite mineral known for forming delicate, prismatic crystal clusters in basaltic cavities. It is notable for its tendency to dehydrate rapidly upon exposure to air, often turning chalky or crumbling into a powder, so collectors should store specimens in a humidified environment.
Is this laumontite?
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 laumontite with a known reference. Laumontite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: white, colorless, yellow, orange, pink, brownish, gray, yellowish, pearl white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed, crystalline, prismatic.
Often confused with
Laumontite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside laumontite
Minerals reported to co-occur with laumontite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₂Si₄O₁₂·4H₂O
- Mohs hardness
- 3-4
- Density
- 2.23-2.41 g/cm³
- Streak
- White
- Luster
- Vitreous to pearly on cleavages
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed, crystalline, prismatic
- Cleavage
- {010}, {110}, perfect
- Fluorescence
- Weak white under SW UV; weak white under LW UV
- Rarity
- Common
- Uses
- Collector, Scientific research
- Host rock
- Of hydrothermal origin, lining cavities in igneous rocks
Where rockhounds find laumontite
3 mapped spotsClassic worldwide localities
- Pine Creek tungsten mine, Bishop, Inyo Co., California, USA
- Drain, Douglas Co., Oregon, USA
- Bergen Hill, Hudson Co., and Paterson, Passaic Co., New Jersey, USA
- Goose Creek quarry, Leesburg, Loudoun Co., Virginia, USA
- Sa̧ca̧râmb (Nagyág), Romania
- St. Gotthard, Ticino, Switzerland
Field-hunting tip
Where it forms: Of hydrothermal origin, lining cavities in igneous rocks. If you start seeing zeolites, apophyllite, datolite in float, you are in the right ground. Typical habit: bladed, crystalline, prismatic. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Michigan, Wisconsin. Start trip planning there.
Common questions
How do you identify laumontite?+
Where is laumontite found?+
Can I find laumontite in the United States?+
What rocks look like laumontite?+
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Find laumontite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
