Banded rhyolite is simply a variation of rhyolite which has crystalised still showing the flow banding which would have been produced by the flowing action of the lava which resulted in forming the rock. These particular rock specimens of banded Rhyolite come from Glen Coe, Scotland. In banded igneous rocks the friction and viscosity of the magma causes phenocrysts and xenoliths within the magma or lava to slow down near the interface and become trapped in a viscous layer. This forms laminar flow, which manifests as a banded, streaky appearance. Available in 3 different sizes and supplied in a card tray with an information label.