Gmelinite-Ca is a member of the zeolite group often found as sharp, rhombohedral crystals in volcanic amygdules. Collectors should look for its distinctive hexagonal habit, which can sometimes appear as complex interpenetrating twins, typically occurring in basaltic environments alongside other zeolites.
Is this gmelinite-ca?
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 gmelinite-ca with a known reference. Gmelinite-Ca sits at Mohs 4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gmelinite-Ca leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gmelinite-Ca typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pink, yellow.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: rhombohedral crystals, sometimes pseudo-hexagonal bipyramids.
Often confused with
Gmelinite-Ca vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside gmelinite-ca
Minerals reported to co-occur with gmelinite-ca. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Na₂,K₂)₄(Al₈Si₁₆O₄₈)·22H₂O
- Mohs hardness
- 4.5
- Density
- 2.05-2.15 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Rhombohedral Crystals, Sometimes Pseudo-hexagonal Bipyramids
- Cleavage
- Distinct On {10-10}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Basaltic Volcanic Cavities
- Typical price
- $15-100 per specimen depending on crystal size and matrix quality
Where rockhounds find gmelinite-ca
Classic worldwide localities
- Cape Blomidon, Nova Scotia, Canada
- Antrim, Northern Ireland
- Victoria, Australia
- Faroe Islands
Field-hunting tip
Look in basaltic volcanic cavities country — that is the host setting where gmelinite-ca typically forms. If you start seeing heulandite, stilbite, analcime in float, you are in the right ground. Field specimens usually show a rhombohedral crystals, sometimes pseudo-hexagonal bipyramids habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gmelinite-ca?+
Where is gmelinite-ca found?+
How much is gmelinite-ca worth?+
What rocks look like gmelinite-ca?+
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Find gmelinite-ca on the map
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