In nature, potassium is found in the Earth's crust, 2.59 % (w/w), in minerals such as sylvite, orthoclase, microcline, and carnallite . The isotopes found in nature are 39K (93.22 %, stable), 40K (0.012 %, T½ = 1.26 · 109 years) and 41K (6.77 %, stable) .
In pure, solid form, potassium exist in a body-centered cubic crystal structure 
Potassium is produced by the reaction of molten Na and KCl :
Na (l) + KCl (l) K (l) + NaCl (l)
The sodium is fed at the bottom of a column and the molten potassium comes out at the top.