INTRODUCTION t is tempting to think of geologists people who study rocks and minerals as sci ence pirates After all much like the buccaneers of old they spend a great deal of time searching for buried treasure In the case of geology however there are no chests filled with money and jew els The riches geologists uncover are made of stone The nature and importance of these earthy trea sures is the focus of this book As the building blocks of the Planet Earth indeed the very stuff of which the world is made minerals and rocks are priceless treasures Beyond that their worth can be measured by their usefulness For instance minerals are important nutri ents that every living thing on Earth must have in order to survive They also make up the various types of rocks that are the components of natural and manmade creations everything from hills and continents to buildings
INTRODUCTION A fossilized fish embedded in rock Michael Med ford National Geographic Image Collection Getty Images
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
INTRODUCTION Anyone wanting to know about the evolution of inorganic or nonliving ele ments of Earth should look to rocks and minerals Fossils on the other hand pro vide a glimpse of a long ago living world Plant leaves primordial sea creatures and the feet of prehistoric mammals all have left imprints in material that has turned to stone The cells of living trees that petrify turning hard as a rock and the buried skele tons of prehistoric creatures are fossils too By studying fossils scientists can tell where the ancestors of today s plants and animals lived how they survived and when certain species became extinct Owning a diamond mine or holding the deed to land that has large deposits of min erals such as copper or iron could make a person rich In general however smaller col lections of minerals rocks and fossils won't make someone a millionaire Yet the wealth of information these Earth components hold makes them true treasures
