What is the Difference Between Stilbite and Heulandite

The key difference between stilbite and heulandite is that stilbite can occur in monoclinic, triclinic, and orthorhombic crystal systems, whereas heulandite occurs in a monoclinic crystal system.

Both stilbite and heulandite are members of the tectosilicate group and fall under the group of zeolites. These are naturally occurring mineral substances.

CONTENTS

1. Overview and Key Difference
2. What is Stilbite 
3. What is Heulandite
4. Stilbite vs Heulandite in Tabular Form
5. Summary – Stilbite vs Heulandite

What is Stilbite?

Stilbite is a zeolite mineral that comes under a series of tectosilicate minerals. There are two forms as stilbite-Ca and stilbite-Na, according to the chemical composition. Among these two forms, stilbite-Ca is the most common form. Stilbite-Ca is a hydrous calcium, sodium and aluminum silicate compound where calcium amount dominates over the sodium amount. On the other hand, in stilbite-Na, the amount of sodium dominates over the calcium amount.

Stilbite comes under the category of tectosilicates and zeolites. It has a monoclinic crystal system. But there can be triclinic or orthorhombic forms as well. The crystal class of stilbite is prismatic, and usually, this mineral appears as a colorless, white, or pink colored substance. It has a brittle nature and the luster is vitreous. Moreover, the fracture of stilbite is conchoidal or uneven and shows a white mineral streak. However, stilbite is transparent to translucent in its diaphaneity. Stilbite can get dissolved and decomposed in hydrochloric acid.

Typically, the crystals of stilbite are thin tabular, flattened parallel to the dominant cleavage. However, we can observe that aggregates of stilbite are sheaf-like or bow-ties, fibrous and globular.

When considering the uses of stilbite, its structure can act as a molecular sieve, which enables it to separate hydrocarbons during the process of petroleum refining.

What is Heulandite?

Heulandite is a type of tectosilicate mineral of the zeolite group, and it is a hydrous calcium and aluminum silicate. There are several types of heulandite, which include heulandite-Ca, heulandite-Na, heulandite-K, heulandite-Sr, and heulandite-Ba. Among these forms, the heulandite-Ca is the most common form.

This mineral substance has a monoclinic crystal system, and its crystal class is prismatic. Heulandite mineral appears in colorless, yellow, green, white, or pale pink colors. It occurs in tabular, parallel aggregates, which has a perfect basal cleavage. This mineral substance has a pearly, vitreous luster and the mineral streak color is white. It can be transparent or translucent.

What is the Difference Between Stilbite and Heulandite?

Both stilbite and heulandite are members of tectosilicate group that comes under the group of zeolites. These are naturally occurring mineral substances. The key difference between stilbite and heulandite is that stilbite can occur in monoclinic, triclinic, and orthorhombic crystal systems, whereas heulandite occurs in a monoclinic crystal system. Moreover, stilbite has a colorless, white, or pink appearance, whereas heulandite has a colorless, yellow, green, white or pale pink appearance. So, this is the difference between stilbite and heulandite in terms of appearance. Besides, stilbite-Ca and stilbite-Na are variations of stilbite while heulandite-Ca, heulandite-Na, heulandite-K, heulandite-Sr, and heulandite-Ba are variations of heulandite.

The below infographic lists the differences between stilbite and heulandite in tabular form for side by side comparison.

Summary – Stilbite vs Heulandite

Both stilbite and heulandite are members of the tectosilicate group and fall under the group of zeolites. These are naturally occurring mineral substances. The key difference between stilbite and heulandite is that stilbite can occur in monoclinic, triclinic and orthorhombic crystal systems, whereas heulandite occurs in a monoclinic crystal system.

Reference:

1. “Stilbite Meanings and Crystal Properties.” Meanings and Crystal Properties – The Crystal Council.

Image Courtesy:

1. “Fluorapophyllite-Stilbite-Ca-indi-52b” By Rob Lavinsky, iRocks.com (CC-BY-SA-3.0) via Commons Wikimedia
2. “Heulandite-160733” By Rob Lavinsky, iRocks.com – (CC-BY-SA-3.0) via Commons Wikimedia