Molybdenum is a chemical element with symbol Mo and atomic number 42. Molybdenum does not exist naturally as a free metal on Earth, but rather in various oxidation states in minerals. The free element, which is a silvery metal with a gray cast, has the sixth-highest melting point among all other elements in the periodic table.
Rhenium is a chemical element with symbol Re and atomic number 75. This heavy element with silvery-white color, is a third-row transition metal in group 7 of the periodic table. Rhenium chemically resembles manganese and technetium, and it is obtained as a by-product of Molybdenum and Copper ore's extraction and refinement.