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
eere CHAPTER SEE EARTH's BUILDING MATERIALS arth s building materials are minerals and rocks Minerals are natural sub stances that combine to form rocks and rocks are the basic unit that make up the A geologist examines a sample of granite using a magnifying loupe InStock Photographic Ltd Photodisc Getty Images IO
EARTH's BULDING MATERIALS solid Earth A rock may be made up of one or more minerals Pure sandstone for example consists only of the mineral quartz Granite is composed chiefly of three minerals quarte feldspar and mica A recipe with different mineral ingredients results in a different kind of rock Scientists who study minerals and rocks work in the fields called mineralogy and petrology Mineralogy includes the study of the physical and chemical properties of minerals their forms and the various ways in which they are distinguished from one another Petrology deals with the origin occurrence composition structure and his tory of rocks Because most rocks consist of minerals the two fields are closely related Both mineralogy and petrology fall within the broader science of geology which is con cerned with the origin of Earth its history its shape the materials forming it and the pro cesses that are acting and have acted on it CHARACTERISTICS OF MINERALS To be classified as a mineral a substance must have an inorganic or nonliving origin and a composition that can be expressed by a chemical formula Its elements may be II
