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Rhyolite is the extrusive equivalent of granite, with a very similar mineral and chemical composition. Rhyolite is extremely fined grained, and individual minerals usually cannot be accurately identified with a microscope. Rhyolites may exhibit flow banding (physical indication of the direction of lava flow) due to the viscous nature of acidic lavas. Occasionally, rhyolite may show phenocrysts, amygdules, and/or spherulites. Rhyolite is acidic (high silica content), and fractures conchoidally (curved, concentric fractures). Rhyolites are commonly found as flows, sills, or dikes.
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