minerai à teneur plus faible

CONT: (...) la découverte d'un nouveau procédé de traitement permettra d'extraire des minerais à teneur plus faible (...)

CONT: The tendency with many metals during this century has been to mine lower and lower grade ores.
CONT: Ore grades are somewhat variable. The lowest grade of working deposit in western countries appears to be ... [a] mine working 0.2% Ni ore. This low grade can be compared with the very high grade sections of some Western Australian deposits that run about 12% Ni. Of course, the overall grade for Australian deposits is less than this because lower grade ore is mined with these high grades.