Mineral

Green Apophyllite and Stilbite on Quartz Cluster

Apophyllite-(K) (KCa4(Si8O20)(F,OH)·8H2O), Stilbite-Ca (NaCa4(Si27Al9)O72·28H2O), Quartz (SiO2)

Apophyllite: Hardness 4.5-5 Mohs, typically colorless to white, sometimes green, yellow, pink. Vitreous luster. Tetragonal crystal system. Perfect basal cleavage. Stilbite: Hardness 3.5-4 Mohs, commonly white, pink, orange, brown. Vitreous to pearly luster. Monoclinic crystal system. Perfect cleavage.…

Identified September 22, 2025More mineral →

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Physical properties

Formation & geological history

Hydrothermal deposits. Apophyllite and Stilbite are typical secondary minerals formed during the late stages of volcanic rock alteration, often found lining cavities and vesicles (geodes or vugs) in basalt and other mafic igneous rocks. Quartz may form as primary crystallization or later hydrothermal alteration within various rock types.

Uses & applications

Primarily a collector's mineral due to its aesthetic crystal formations and color variations. High-quality clusters are sought after by mineral enthusiasts and for decorative purposes. Apophyllite has some minor industrial uses in catalysis and zeolites.

Geological facts

Apophyllite, especially the green variety (often due to vanadium content), is highly prized for its vibrant color and terminated crystals. Stilbite is a member of the zeolite group, known for its ability to exchange ions and absorb water. Quartz is one of the most abundant minerals in the Earth's crust and forms the basis for many different mineral varieties.

Field identification & locations

Look for distinct, transparent to translucent, pyramidal or tabular crystals of quartz, clear to green square-prismatic crystals of apophyllite, and sheaf-like or radiating aggregates of stilbite, often white or peachy, all growing together on a matrix. This combination is characteristic of finds in India, particularly the Deccan Traps region.

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