Minerals · common

Heulandite

Heulandite is a calcium- and sodium-bearing zeolite mineral, part of a group known for its coffin-shaped monoclinic crystals with a distinctive pearly luster on one prominent cleavage face. It typically forms as a secondary mineral filling vesicles and fractures in basaltic and volcanic rocks, alongside other zeolites deposited by cooling hydrothermal fluids. Heulandite is named after English mineral collector Henry Heuland, whose collection contributed significantly to early zeolite mineralogy.

Photo: Robert M. Lavinsky · Wikimedia Commons · CC BY-SA 3.0

Heulandite properties at a glance

Type	Minerals
Chemical formula	(Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O
Mohs hardness	3.5–4
Crystal system	Monoclinic
Luster	Vitreous, pearly on cleavage
Streak	White
Cleavage	Perfect, one direction
Fracture	Uneven
Specific gravity	2.1–2.2
Transparency	Transparent to translucent
Common colors	White, Colorless, Pink, Red, Brown, Yellow
Rarity	common

Geology & background

Heulandite crystallizes from hydrothermal fluids circulating through the cavities of basalt and related volcanic rocks as the host lava cools, filling amygdules and veins alongside stilbite, chabazite, and apophyllite in classic zeolite assemblages. The Deccan Traps of India are today the world's premier source of large, well-formed heulandite crystals, often found in dramatic association with stilbite's bow-tie sheaves, while other notable localities include Iceland, the Faroe Islands, and Nova Scotia's Bay of Fundy basalts. Heulandite can also form in some low-grade metamorphic and hydrothermally altered sedimentary rocks.

Collectors particularly seek heulandite for its flattened, coffin-shaped or diamond-shaped crystals, which often display a striking pearly sheen on the perfect cleavage face that distinguishes zeolites from most other mineral groups. Because Indian material has become widely available since the late twentieth century, heulandite is now one of the more accessible zeolites for building a representative collection, with color varieties ranging from colorless and white to peach, orange, and red depending on iron content in the host basalt.

How to identify Heulandite

Heulandite is commonly colorless, white, pink, peach, or brick-red, with a vitreous luster on most faces but a distinctive pearly luster on its perfect cleavage face, and it has a white streak. It has a hardness of 3.5 to 4 and one perfect cleavage direction, typically forming flattened, coffin-shaped monoclinic crystals that are a hallmark of the mineral. It is easily confused with the related zeolite stilbite, but heulandite's crystals are more tabular and blocky compared to stilbite's characteristic sheaf-like or bow-tie aggregates of thinner blades.

Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
Use multiple photos when possible, including a fresh surface and a close view of texture.

Where Heulandite is found

Reported from multiple localities worldwide; verify locality against specimen provenance when available.

How much is Heulandite worth?

Entry-level specimen	$2
Typical collector specimen	$20
Premium specimen	$150+

Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.

Common uses

Collector specimens
Education
Field identification
Industrial or lapidary use when suitable

Interesting facts

Heulandite's distinctive flattened, coffin-like crystal shape is one of the most recognizable habits among the roughly fifty known natural zeolite species.
The mineral is named for Henry Heuland, a nineteenth-century English mineral dealer and collector whose specimens helped establish the species.
India's Deccan Traps, a vast basalt plateau formed by massive volcanic eruptions around 66 million years ago, now supply most of the fine heulandite specimens seen in mineral collections worldwide.