igneous
Spherulitic Rhyolite / Leopard Skin Rhyolite
Extrusive felsic igneous rock with spherulites
Hardness: 6-7 on the Mohs scale; Color: Dark brown or black base with contrasting light green, yellow, or grey spherulitic spots; Luster: Vitreous to dull; Crystal structure: Microcrystalline to cryptocrystalline groundmass with radial crystalline spherulites; Cleavage: None
- Hardness
- 6-7 on the Mohs scale
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 6-7 on the Mohs scale; Color: Dark brown or black base with contrasting light green, yellow, or grey spherulitic spots; Luster: Vitreous to dull; Crystal structure: Microcrystalline to cryptocrystalline groundmass with radial crystalline spherulites; Cleavage: None
Formation & geological history
Formed through the rapid cooling of silica-rich lava at or near the Earth's surface, where minerals crystallized radially outward from a central point to form distinctive round spherulites during the volcanic process.
Uses & applications
Used primarily as a decorative stone, in lapidary arts, tumbled stones, cabochons for jewelry, and as a collectible specimen.
Geological facts
The distinctive circular patterns are known as spherulites, which form when high-temperature volcanic glass or silica-rich melt devitrifies and minerals like quartz and feldspar grow outward in spherical clusters.
Field identification & locations
Can be identified in the field by its dense, fine-grained volcanic matrix marked by characteristic contrasting circular or 'leopard-like' spots. Found in volcanic regions worldwide.
