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
INVESTIGATING MINERALs Rocks AND Fossus known as building stones They are removed from the earth by a process called quarrying Buried treasure lies in the rocks Some of their minerals are highly valued jewels such as diamonds emeralds and rubies Gold and silver iron copper and the miracle metals of the atomic age uranium and thorium are among the minerals essential to modern civilization These are taken from the earth by mining IDENTIFYING MINERALS AND RoCKS Scientists identify minerals by certain impor tant properties These include hardness cleavage and color Other means of dis tinguishing a mineral are its elasticity and strength specific gravity radioactivity and thermal electrical and magnetic proper ties Luminescence or the emission of light Sometimes permits rapid detection of some minerals including some uranium ores The hardness of minerals is usually stated in terms of the Mohs scale The scale ranks minerals as follows from softest to hardest D talc 2 gypsum 3 calcite 4 fluorite 5 apatite 6 orthoclase quartz 8 topaz 14
EARTH's BULDING MATERIALS 9 corundum IO diamond The mineral with the higher number can scratch anything beneath it or equal to it in hardness Thus a diamond can scratch everything A mineral that will scratch apatite but not orthoclase has a rank in hardness of between 5 and 6 Purple fluorite crystal showing multisided planes or cleavage Shutterstock com 15
