Rhenium

In nature, rhenium is found in the Earth's crust, 0.001 ppm, in minerals such as gadolinite, molydenite, columbite, rare earth minerals and some sulfide ores [4]. The isotopes found in nature are ¹⁸⁵Re (37.07 %, stable) and ¹⁸⁷Re (62.93 %, T_½ ~10¹¹ years) [4].

In pure solid form, rhenium exist in close-packed hexagonal crystal structure [4]