Claim: Lightning rods can be made from metals.

Copper is a chemical element with symbol Cu -LRB- from cuprum -RRB- and atomic number 29 . It is a soft , malleable , and ductile metal with very high thermal and electrical conductivity . A freshly exposed surface of pure copper has a reddish-orange color . Copper is used as a conductor of heat and electricity , as a building material , and as a constituent of various metal alloys , such as sterling silver used in jewelry , cupronickel used to make marine hardware and coins , and constantan used in strain gauges and thermocouples for temperature measurement .   Copper is one of the few metals that occur in nature in directly usable metallic form as opposed to needing extraction from an ore . This led to very early human use , from c. 8000 BC . It was the first metal to be smelted from its ore , c. 5000 BC , the first metal to be cast into a shape in a mold , c. 4000 BC and the first metal to be purposefully alloyed with another metal , tin , to create bronze , c. 3500 BC .   In the Roman era , copper was principally mined on Cyprus , the origin of the name of the metal , from aes сyprium -LRB- metal of Cyprus -RRB- , later corrupted to сuprum , from which the words copper -LRB- English -RRB- , cuivre -LRB- French -RRB- , Koper -LRB- Dutch -RRB- and Kupfer -LRB- German -RRB- are all derived . The commonly encountered compounds are copper -LRB- II -RRB- salts , which often impart blue or green colors to such minerals as azurite , malachite , and turquoise , and have been used widely and historically as pigments . Copper used in buildings , usually for roofing , oxidizes to form a green verdigris -LRB- or patina -RRB- . Copper is sometimes used in decorative art , both in its elemental metal form and in compounds as pigments . Copper compounds are used as bacteriostatic agents , fungicides , and wood preservatives .   Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase . In molluscs and crustaceans , copper is a constituent of the blood pigment hemocyanin , replaced by the iron-complexed hemoglobin in fish and other vertebrates . In humans , copper is found mainly in the liver , muscle , and bone . The adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight .