Heulandite-K is a distinct member of the zeolite group often recognized by its characteristic coffin-shaped monoclinic crystals. It is typically found lining cavities in volcanic basalt and is highly prized by collectors for its aesthetic formation and crystal clarity.
Is this heulandite-k?
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 heulandite-k with a known reference. Heulandite-K sits at Mohs 3.5-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Heulandite-K leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Heulandite-K typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pink, orange, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals with coffin-shaped faces.
Often confused with
Heulandite-K vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside heulandite-k
Minerals reported to co-occur with heulandite-k. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na,Ca)₅Al₅(Si,Al)₁₇O₄₄·18H₂O
- Mohs hardness
- 3.5-4
- Density
- 2.1-2.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals with Coffin-shaped Faces
- Cleavage
- Perfect Basal
- Rarity
- Uncommon
- Uses
- Collector, Decorative
- Host rock
- Basaltic Cavities, Hydrothermal Veins, And Volcanic Rocks
- Typical price
- $10-100 per specimen depending on size and crystal quality
Where rockhounds find heulandite-k
Classic worldwide localities
- India
- Iceland
- USA
- Italy
Field-hunting tip
Look in basaltic cavities, hydrothermal veins, and volcanic rocks country — that is the host setting where heulandite-k typically forms. If you start seeing stilbite, apophyllite, calcite in float, you are in the right ground. Field specimens usually show a tabular crystals with coffin-shaped faces habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify heulandite-k?+
Where is heulandite-k found?+
How much is heulandite-k worth?+
What rocks look like heulandite-k?+
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Find heulandite-k on the map
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