5.8" Polished Rainforest Jasper (Rhyolite) Slab - Australia

Rainforest jasper is the trade name for a very colorful type of rhyolite. It was formed when the long extinct Mount Hay volcano near Queensland, Australia erupted about 120 million years ago and subsequent silica-rich fluids deposited into gaps and cavities. Rainforest jasper gets its name because the mixture of green, red, yellow, brown, and orange colorations reminds people of a rainforest canopy. The spherical cavities (orbs) are lined with often lined with opal and tridymite, and filled with chalcedony.

A rhyolite is a volcanic rock characterized by a high silica content that forms from eruptions of granitic magmas. Granitic magmas are very dense, which causes them to cool more slowly: this allows more time for large crystalline structures called phenocrysts to form. These phenocrysts are typically silica-based minerals such as quartz and chalcedony, and are what give rainforest jasper its unique appearance.