Mercury (element)
Mercury is a rare metal. It is about as common as silver. Mercury is not expensive like silver because the mercury is very easy to get from the places where it is found. Mercury can be found in elemental (liquid) form in nature, but this is not common. Mercury as an element is the only liquid that is recognized as a mineral by  the International Mineralogical Association. It is most often found in the form of cinnabar, a mercury(II) sulfide mineral. The biggest deposits of cinnabar used to be found in Spain, but now are found in China. It also occurs in other minerals like calomel, a mercury(I) chloride mineral.