igneous
Wonderstone (Banded Rhyolite)
Rhyolite (Silicon Dioxide with Iron Oxide impurities)
Hardness: 6-7 (Mohs scale), Color: Bands of red, pink, tan, and white, Luster: Dull to earthy when raw, Crystal Structure: Microcrystalline (Aphanitic), Specific Gravity: ~2.4-2.6
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Bands of red, pink, tan, and white, Luster: Dull to earthy when raw, Crystal Structure: Microcrystalline (Aphanitic), Specific Gravity: ~2.4-2.6
Formation & geological history
Formed from volcanic eruptions of silica-rich lava that cools rapidly near the surface. The distinct banding is caused by rhythmic precipitation of iron oxides (Liesegang rings) within the porous volcanic ash or rock over millions of years.
Uses & applications
Commonly used for lapidary work, making cabochons, decorative carvings, landscaping features, and as a popular specimen for mineral collectors.
Geological facts
The striking concentric patterns are called Liesegang rings; they are a chemical phenomenon and not annual growth rings like a tree. Despite its name, wonderstone is a volcanic rock, not a mineral.
Field identification & locations
Identified by its distinctive swirling colorful bands and smooth, almost glass-like fracture where broken. Commonly found in the Great Basin of the Western United States, particularly Nevada and Utah.
