The Greek island of Thera or Santorini is largely composed of this rock. Ignimbrites are structures composed of chunks of this rock floating in a finer-grained matrix, and heavily compacted fragments of it are known as fiamme. When combined with lime it can form the industrial cement known as pozzolan. Along with tephra it forms the majority of a cinder cone. In contrast to scoria, it is felsic and forms from trachytes and rhyolites, and is often accompanied by the much 
The Greek island of Thera or Santorini is largely composed of this rock. Ignimbrites are structures composed of chunks of this rock floating in a finer-grained matrix, and heavily compacted fragments of it are known as fiamme. When combined with lime it can form the industrial cement known as pozzolan. Along with tephra it forms the majority of a cinder cone. In contrast to scoria, it is felsic and forms from trachytes and rhyolites, and is often accompanied by the much more slowly-cooling obsidian. FTP, identify this pyroclastic igneous rock which can float in water and is often found in heavy-duty soaps.
The Greek island of Thera or Santorini is largely composed of this rock.
pumice