mineral

Heulandite with Stilbite

Heulandite-Ca ((Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O) and Stilbite-Ca (NaCa4(Si27Al9)O72·28H2O)

Hardness: 3.5-4 (Mohs); Color: White, cream, or peach bladed crystals on a darker matrix; Luster: Pearly to vitreous; Crystal Structure: Monoclinic; Cleavage: Perfect in one direction; Specific Gravity: 2.1-2.2

Hardness: 3
Color: White, cream, or peach bladed crystals on a darker matrix
Luster: Pearly to vitreous

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal activity in the cavities (vesicles) of volcanic rocks, particularly basalt. These secondary minerals precipitate from low-temperature circulating fluids as the lava cools. Most famous specimens are from the Cretaceous/Eocene Deccan Traps.

Uses & applications

Primarily used as geological specimens for collectors and educational purposes; zeolites like these are also studied for their molecular sieve properties in industry.

Geological facts

Heulandite and Stilbite are both members of the Zeolite group. The peach-colored 'bow-tie' or bladed formation seen in the image is a signature habit for Stilbite. They often form in the same vugs as Apophyllite.

Field identification & locations

Identify in the field by the distinct 'sheaf-like' or 'bow-tie' crystal clusters and pearly luster on cleavage faces. Commonly found in the Pashan Hills and Jalgaon regions of India, as well as Iceland and Scotland. Best found within gas bubbles in basaltic flows.

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