Roasted concentrates (261310) have been thermally oxidized — typically converting molybdenite (MoS₂) to molybdic oxide (MoO₃) — and are classified separately from unroasted concentrates (261390), which retain the sulfide mineral form. The distinction matters because roasted material is a more processed intermediate and may carry a different duty rate.

These countries host large porphyry copper deposits where molybdenum is recovered as a co-product, giving them structural cost advantages. Supply from Armenia and the Netherlands also appears in US import data, the latter often reflecting re-export or processing trade rather than primary mining.