Prospect Resources (ASX:PSC) said metallurgical testwork on primary sulfide samples from the Nyungu Central deposit, at the Mumbezhi copper project in Zambia, returned high-grade saleable copper concentrates with excellent recoveries, according to a Monday Australian bourse filing.

A representative fresh composite sample achieved a copper concentrate with 24.6% grade of copper and 9,000 parts-per-million of cobalt at 96.2% copper recovery after a single cleaning stage. After two cleaning stages, a copper concentrate grading 33.3% of copper and 2,800 ppm grade of cobalt was produced with 90.1% recovery of copper.

Test work on transitional material from the Nyungu Central deposit, along with fresh sulfide material from the Kabikupa deposit, is currently being conducted.

Its shares fell 4% on Monday's close.