Hafnium

Hafnium is found in the Earth's crust, 5 ppm (w/w), in the zirconium containing mineral [4]. The isotopes found in nature are ¹⁷⁴Hf (0.163 %, T_½ = 2 · 10¹⁵ years), ¹⁷⁶Hf (5.21 %, stable), ¹⁷⁷Hf (18.56 %, stable), ¹⁷⁸Hf (27.1 %, stable), ¹⁷⁹Hf (13.75 %, stable) and ¹⁸⁰Hf (32.22 %, stable) [4].

In pure form, hafnium occurs in hexagonal crystal structure [4]