igneous
Orbicular Rhyolite (Rainforest Jasper)
Rhyolite containing Spherulites (SiO2 with impurities)
Hardness: 6.5–7 on Mohs scale; Color: Cream, tan, and green groundmass with dark grey or blue orbicular patches; Luster: Dull to waxy; Texture: Fine-grained with rounded inclusions; Cleavage: None.
- Hardness
- 6
- Luster
- Dull to waxy
Identified More igneous →
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Cream, tan, and green groundmass with dark grey or blue orbicular patches; Luster: Dull to waxy; Texture: Fine-grained with rounded inclusions; Cleavage: None.
Formation & geological history
Formed from rapid cooling of silica-rich volcanic lava where bubbles or seeds allow minerals to crystallize in radial, spherical patterns called spherulites. These deposits are typically associated with volcanic activity from the Cenozoic era.
Uses & applications
Primarily used for ornamental purposes, including stone carvings, cabochons for jewelry, and as decorative pocket stones for collectors.
Geological facts
Also known as 'Rainforest Jasper' despite not being a true jasper (which is sedimentary). The circular 'eyes' or 'orbs' are actually clusters of radiating crystal needles, usually quartz or feldspar.
Field identification & locations
Identify by looking for distinct orb-like or circular patterns within a fine-grained volcanic matrix. Commonly found in Western Australia and parts of the United States like Oregon. Collectors should look for high contrast between the orbs and the background rock.
