A lump of pure gold the size of a matchbox can be flattened into a sheet the size of a tennis court

gold

Gold is malleable, so it can be flattened into extremely thin sheets. One ounce of gold may be hammered thin enough to cover more than 9 square meters (96.9 square feet) of a surface. The gold leaf may be only 0.18 microns (seven millionths of an inch) thick; a stack of 7,055 sheets would be no thicker than a dime.