igneous rocks / minerals are formed by magma / lava cooling / crystallizing & pumice is a kind of igneous rock ->  pumice is formed by lava cooling  if something is formed by a material changing then that something is formed from that material & lava is a kind of material ->  if something is formed by lava changing then that something is formed from lava  if something is formed by lava changing then that something is formed from lava & cooling is a kind of change ->  if something is formed by lava cooling then that something is formed from lava  pumice is formed by lava cooling & if something is formed by lava cooling then that something is formed from lava ->  pumice is formed from lava  a volcano is a source of magma / lava & usually something can be found near a source in greater concentrations ->  usually lava can be found near a volcano  usually lava can be found near a volcano & if something usually happens then that something is likely to happen ->  lava can likely be found near a volcano  pumice is formed from lava & lava can likely be found near a volcano -> pumice is likely formed near a volcano