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
INVESTIGATING MINERALs Rocks AND Fossus metallic or nonmetallic Most minerals have a crystalline structure By this definition the resin amber and the fuels coal petroleum and natural gas are not true minerals These substances were formed from organic substances animal or vege table matter that once lived on Earth The important metallic and nonmetal lic mineral beds that are mined today were deposited over long periods of geologic time as a result of such natural phenomena as weathering and erosion Other processes contributing to the concentration of minerals in the earth are sedimentation precipitation and evaporation of water bodies as well as the circulation of groundwater Minerals are essential to the life of plants and animals Most plants get minerals from the soil Animals including humans obtain them from plants vegetables and fruits or from the milk eggs and meat of plant eating animals THE ABUNDANCE OF Rocks Rock makes up the solid crust of Earth Beneath the crust are pockets of molten rock called magma Certain hard substances formed from the remains of animals and 12
EARTH's BuLDING MATERIALS Black granite being mined in a Zimbabwe quarry Desmond Kwandel AFP Getty Images plants are also called rock Coal which is composed of plant material is an example Limestone contains the shells and skele tons of sea creatures and limy masses built by plants The soil is made up largely of rock that has been broken down by weathering One kind of rock is eaten every day This is salt a rock composed of the mineral halite Granite lime stone sandstone slate and marble are rocks 13
