Typical market specifications
Columbite on the international market generally contains a minimum of 50% Nb2O5. The value is based on the combined Nb2O5+Ta2O5 content payable entirely as Nb2O5, there is no premium for the Ta2O5 content.
The tantalum and niobium minerals often contain somewhat elevated levels of naturally occurring thorium and uranium, usually high enough for them to be classified as radioactive for handling and transport. It is incumbent on any producer or trader to also analyse for Th and U in order to demonstrate whether the material is radioactive or not. As a guide, these elements are of concern for the purpose of mining and handling at levels above 1 Bq/g, a level obtained from e.g. 0.013% ThO2 plus 0.0048% U3O8, whereas for transport the levels of concern are an order of magnitude higher, i.e.10 Bq/g or 0.13% ThO2 plus 0.048% U3O8.