Protactinium is a silvery metal, that is shiny, malleable and ductile, that tarnishes in air .
In nature, protactinium is found in the Earth's crust, as decay products from 238U . Protactinium has no stable isotopes, but the isotopes found in nature are 231Pa (T½ = 3.276 · 104 years), 234Pa (T½ = 6.75 hrs.) and 234mPa (T½ = 1.17 min.) .
In pure solid form, protactinium exist in a body-centered tetragonal crystal form