Rhyolite is expelled from volcanoes as larva.
This sample is technically ‘porphyritic rhyolite’ because it has a mix of large & small crystals. The large crystals are called phenocrysts and the smaller crystals make up the background colour. It has the same chemistry as granite, but granite hardens within the crust below volcanoes.
Igneous. Erupted from volcanoes as a thick larva.
Size: Hand specimen.
Demonstrates erosion to a smooth oval shape due to movement down rivers and coastline.
Images are examples of specimens only. Sizes and shapes may vary.