You know what else is hard
Diamond, it is the only gem made of a single element: It is typically about 99.95 percent carbon. The other 0.05 percent can include one or more trace elements, which are atoms that aren't part of the diamond's essential chemistry. Some trace elements can influence its color or crystal shape. Next, Tungsten, or wolfram, metallic chemical element, one of the transition elements, chemical symbol W, atomic number 74. Exceptionally strong, white to grayish, and brittle, it has the highest melting point (6,170 °F [3,410 °C]), greatest high-temperature strength, and lowest thermal expansion coefficient of any metal.