Investigating Minerals, Rocks, and Fossils

Investigating Minerals, Rocks, and Fossils — page 3
INVESTIGATING MINERALs Rocks AND Fossus and fine sculptures When polished and cut some rocks are transformed into valuable gemstones These are often placed in set tings of gold and silver which are precious metals made from native minerals Even in their stony silence rocks are able to tell an interesting story For instance sedi mentary rocks are formed when several layers of material sand mud and tiny pebbles settle on top of one another and then are squeezed together by pressure and cemented by dissolved minerals The layers called strata remain visible once the rock has been formed Using the strata like a timeline scientists are able to piece together the geologic history of the location where the rock was discovered Rocks that are formed when minerale crys tals within super hot lava or magma cool are called igneous rocks The texture and amount of crystals in igneous rock provide clues about volcanic action underground and how long it took magma to cool and form structures such as mountains Likewise metamorphic rocks which are formed when sedimentary or igneous rocks undergo changes to their shape or mineral structure reveal how hot and pressurized it was deep beneath Earth's surface during certain peri ods of