RocksdayHeulandite vs Stilbite
How to tell them apart
A zeolite forming flat, coffin-shaped crystals with a pearly shine.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
A zeolite that forms peach-colored, bow-tie shaped sheaves of crystals in volcanic cavities.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Key differences
- Stilbite forms bow-tie bundles.
- Heulandite forms coffin-shaped single crystals, not sheaves.
Side by side
| Property | Heulandite | Stilbite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3.5–4 | 3.5–4 |
| Luster | Vitreous to pearly | Vitreous to pearly |
| Streak | White | White |
| Colors | White, Orange, Pink, Green | Orange, White, Pink |
| Crystal system | Monoclinic | Monoclinic |
| Specific gravity | 2.1–2.2 | 2.1–2.2 |
| Formula | (Ca,Na)₂₋₃Al₃(Al,Si)₂Si₁₃O₃₆·12H₂O | NaCa₄(Si₂₇Al₉)O₇₂·28H₂O |
| Found in | Pune, India; Iceland | Pune, India; Bay of Fundy, Nova Scotia |
Properties that are the same for both are grayed out.
How to identify heulandite
- Tabular crystals shaped like coffins.
- Pearly luster on the large flat face.
- Soft and light.
Crystal system: Monoclinic
Full Heulandite guide →How to identify stilbite
- Bow-tie or wheat-sheaf crystal bundles.
- Peach to white with a pearly sheen.
- Soft and light.
Crystal system: Monoclinic
Full Stilbite guide →More comparisons
Could you tell them apart from a blurry close-up?
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