Identifying Rocks Igneous Rocks - Formation Magma is ejected from earth’s core Crystals form in cooling magma Crystals interlock into masses known as igneous rocks Igneous Rocks - Identification the interlocking texture of the grains the presence of vesicules (holes) in extrusive igneous rocks may be dark-colored and heavy may display two grain sizes, one much larger than the other Sedimentary Rocks - Formation Other rocks (igneous, metamorphic) or shells are weathered over time Can be formed from compaction of these sediments …or can be formed by crystallization of dissolved minerals Sedimentary Rocks - ID grains cemented together the presence of fossils light-colored and light weight may display interlocking grains but is very light weight Layers! Metamorphic Rocks - Formation “Metamorphosis” = change Sedimentary or Igneous Rocks that have been changed by intense heat or pressure Metamorphic Rocks - ID the interlocking texture of large grains foliation (layering) layers likely “bent” banded light and dark colors