Heulandite
Heulandite group
Uncommon · (Na,Ca,K)₅₋₆(Al₈₋₉Si₂₇₋₂₈O₇₂)·nH₂O
A zeolite of basalt cavities, growing in coffin-shaped tablets with a pearly sheen on the cleavage. Like every zeolite it holds water loosely in an open framework, and gives it up on gentle heating.
Identity
- Formula
- (Na,Ca,K)₅₋₆(Al₈₋₉Si₂₇₋₂₈O₇₂)·nH₂O
- Chemical class
- Silicate
- Members
- Heulandite-Ca, Heulandite-Na, Heulandite-K, Heulandite-Sr, Heulandite-Ba
- Mineral group
- Analcime, Natrolite, Stilbite
- Also known as
- Lincolnite
Crystallography
- Crystal system
- Monoclinic
- Habits
- Tabular, Prismatic
- Fracture
- subconchoidal to uneven
Physical properties
- Mohs hardness
- 3.5
- Density
- 2.2 g/cm³
- Luster
- Pearly, Vitreous
- Colors
- white, reddish white, grayish white, brownish white, yellow
- Streak
- white
- Transparency
- Transparent, Translucent
Geology
- Origins
- Igneous, Hydrothermal
- Host rocks
- Volcanic rock
- Associated minerals
- Stilbite, Natrolite, Apophyllite, datolite, Calcite
- Geography
- India, Iceland, USA
Classification
- Rarity
- Uncommon
- Gem quality
- No
Sources
- Heulandite Subgroup. Mindat.org (Hudson Institute of Mineralogy).
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- Heulandite-Ca. Mindat.org (Hudson Institute of Mineralogy).
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Heulandite. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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