Analcime is a member of the zeolite group most easily identified by its distinctive trapezohedral crystal habit, which often mimics the shape of a garnet. It is typically found lining amygdaloidal cavities in basaltic rocks and volcanic formations. Collectors prize sharp, glassy crystals that occur in association with other delicate zeolite minerals.
Is this analcime?
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 analcime with a known reference. Analcime sits at Mohs 5-5.5, 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.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray, pink, greenish, grayish white, greenish white, yellowish white, reddish white.
- 5Look at form & habitCrystal system: cubic. Typical habit: euhedral crystals, granular, massive.
Often confused with
Analcime vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside analcime
Minerals reported to co-occur with analcime. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na(AlSi₂O₆)·H₂O
- Mohs hardness
- 5-5.5
- Density
- 2.24-2.29 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
- Crystal habit
- Euhedral crystals, granular, massive
- Cleavage
- Very poor on {100}
- Fluorescence
- Green blue white under SW UV; green under LW UV
- Rarity
- Common
- Uses
- Collector, Industrial (molecular sieve)
- Host rock
- In the groundmass or vesicles of silica-poor intermediate and mafic igneous rocks, typically basalts and phonolites, from late-stage hydrothermal solutions, or disseminated due to deuteric alteration
Where rockhounds find analcime
5 mapped spotsClassic worldwide localities
- Lake Superior district, Houghton Co., Michigan, USA
- Cornwall, Lebanon Co., Pennsylvania, USA
- Bergen Hill, Hudson Co., and West Paterson, Passaic Co., New Jersey, USA
- Table Mountain, Jefferson Co., Colorado, USA
- Aci Castello, Cyclopean Islands, and from Val di Fassa and Alpe di Siusi, Trentino-Alto Aldige, Italy
- Kotchechovmo, Krasnoyarski Territory, Russia
Field-hunting tip
Where it forms: In the groundmass or vesicles of silica-poor intermediate and mafic igneous rocks, typically basalts and phonolites, from late-stage hydrothermal solutions, or disseminated due to deuteric alteration. If you start seeing zeolites, prehnite, calcite in float, you are in the right ground. Typical habit: euhedral crystals, granular, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey, Maine. Start trip planning there.
More analcime photos
Common questions
How do you identify analcime?+
Where is analcime found?+
Can I find analcime in the United States?+
What rocks look like analcime?+
What minerals are found with analcime?+
What kind of rock does analcime form in?+
What is analcime used for?+
Find analcime on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
