The rarest metal on Earth?

Rhenium can be considered the rarest metal on Earth. Its appearance was predicted by Mendeleev in 1870, but it was discovered only in 1925. Rhenium is named after the German river Rhine. Its value exceeds that of platinum. Rhenium is one of the most refractory metals, but in spite of this it is rather ductile; heat resistant; very resistant to corrosion and oxidation processes. Its use is limited due to its high cost – in the second half of the 20th century, a kilogram of rhenium cost about $ 1,300.