Both tantalum (coltan/columbite-tantalite) and niobium (columbite, pyrochlore) ores fall under 261590 without further subdivision at the HS6 level. Customs classification does not require separating them at this heading; however, export controls and conflict-mineral due-diligence requirements — particularly for tantalum from certain regions — may require detailed documentation of mineral identity and origin.

Zircon sand classified here is a naturally occurring mineral concentrate and is generally not subject to nuclear-specific import controls at this stage. However, further-processed zirconium metal or zirconium alloys intended for nuclear reactor use may fall under export/import licensing regimes administered by the Nuclear Regulatory Commission. Classification and end-use should be reviewed carefully for processed forms.