mineral

Tumbled prehnite (probable)

Prehnite, Ca₂Al₂Si₃O₁₀(OH)₂; possibly epidote- or chlorite-bearing

AI-generated identification · may be incorrect

Pale green, translucent, glassy to pearly tumbled stone with cloudy inclusions and rounded edges. Mohs hardness 6–6.5; orthorhombic crystal structure; poor cleavage; specific gravity about 2.80–2.95.

Identified August 9, 2026More mineral →

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Physical properties

Formation & geological history

Forms in cavities and fractures of basalt and other mafic volcanic rocks through low-temperature hydrothermal alteration, commonly with zeolites, quartz, calcite, or epidote. Most specimens are Cenozoic to older, depending on locality.

Uses & applications

Used as a decorative and collectible gemstone, cabochon, bead, and tumbled stone; rarely used industrially because attractive material is limited.

Geological facts

Prehnite is among the classic minerals of basalt cavities and may display attractive botryoidal growth. The gray-green internal patches could indicate epidote, chlorite, or inclusions rather than pure prehnite.

Field identification & locations

Common sources include South Africa, Australia, India, China, Scotland, and the United States. Confirm by its pale green color, translucent waxy appearance, hardness, and association with basalt minerals; visual identification alone is not definitive.