Mercury (Hg)

Mercury is unique, as it is the only metal that is liquid at room temperature

Mercury is unique, as it is the only metal that is liquid at room temperature, having a melting point of - 40 C, and a boiling point of 357 C. This silvery liquid metal is very dense, yet has a high surface tension that causes is to form tiny little perfect spheres in the pores of the rocks it is found in. When frozen, mercury forms crystals in the rhombohedral system at low pressure, and in the tetragonal system at high pressure.