<P> The Washington Monument is a hollow Egyptian style stone obelisk with a 500 - foot ( 152.4 m ) tall column and a 55 - foot ( 16.8 m ) tall pyramidion . Its walls are 15 feet ( 4.6 m ) thick at its base and 1 ⁄ feet ( 0.46 m ) thick at their top . The marble pyramidion has thin walls only 7 inches ( 18 cm ) thick supported by six arches , two between opposite walls that cross at the center of the pyramidion and four smaller corner arches . The top of the pyramidion is a large marble capstone with a small aluminum pyramid at its apex with inscriptions on all four sides . The lowest 150 feet ( 45.7 m ) of the walls , constructed during the first phase 1848 -- 54 , are composed of a pile of bluestone gneiss rubble stones ( not finished stones ) held together by a large amount of mortar with a facade of semi-finished marble stones about 1 ⁄ feet ( 0.4 m ) thick . The upper 350 feet ( 106.7 m ) of the walls , constructed during the second phase 1880 -- 84 , are composed of finished marble surface stones , half of which project into the walls , partially backed by finished granite stones . </P>
<P> The Washington Monument is a hollow Egyptian style stone obelisk with a 500 - foot ( 152.4 m ) tall column and a 55 - foot ( 16.8 m ) tall pyramidion . Its walls are 15 feet ( 4.6 m ) thick at its base and 1 ⁄ feet ( 0.46 m ) thick at their top . The marble pyramidion has thin walls only 7 inches ( 18 cm ) thick supported by six arches , two between opposite walls that cross at the center of the pyramidion and four smaller corner arches . The top of the pyramidion is a large marble capstone with a small aluminum pyramid at its apex with inscriptions on all four sides . The lowest 150 feet ( 45.7 m ) of the walls , constructed during the first phase 1848 -- 54 , are composed of a pile of bluestone gneiss rubble stones ( not finished stones ) held together by a large amount of mortar with a facade of semi-finished marble stones about 1 ⁄ feet ( 0.4 m ) thick . The upper 350 feet ( 106.7 m ) of the walls , constructed during the second phase 1880 -- 84 , are composed of finished marble surface stones , half of which project into the walls , partially backed by finished granite stones . </P>
what metal is on top of the washington monument
what metal is on top of the washington monument
aluminum
aluminum