Occurrence, isolation & synthesis

Thorium is a grayish-white, lustrous metal, that is somewhat ductile and malleable [4].


In nature, thorium is found in the Earth's crust, 8-15 ppm, in minerals such as thorite, thorianite, orangite, yttocrasite, and monazite. Of these, monazite is the major commercial source [4]. Thorium has no stable isotopes, but the primary isotope found in nature is 232Th (~100 %, T½ = 1.4 · 1010 years). Minor amounts of other isotopes from degradation can be found: 228Th from 232Th, 227Th and 231Th from 235U and 230Th and 234Th from 238U [4].

In pure solid form, thorium exist in the following forms:
α-form: face-centered cubic crystal at < 1360 °C [4]
β-form: body-centered cubic crystal at > 1360 °C [4]