Applied Mineralogy of Refractory Copper Ores from the Nchanga Mine in the Copperbelt of Northern Zambia


Certain copper ores from the Nchanga Copper Mine in the northern Zambia Copperbelt are refractory with respect to conventional beneficiation techniques. This paper reviews recent study of those ores to determine their mineralogy, textures and nature of copper occurrence. Two suites of refractory ores were selected for study: 1. samples of stockpiled ores from an open pit, and 2. drill core samples from copper ores. Both sample suites are from the upper orebody at Nchanga and contain about 0.3-1.4 per cent copper as determined by atomic absorption, but they represent separate stratigraphic, mineralogical and beneficiation problems. Ore microscopic examination showed that fine-grained copper sulfides are totally lacking from both suites of refractory ores. Petrographic study found malachite in the refractory ores from the open pit, but that malachite probably is post-mine. The opaque mineralogy of the open pit refractory ores is dominated by goethite that occurs mostly as pseudomorphic grains after pyritohedral pyrite crystals that average 200-250 μm across. Haematite occurs as bands within or as outer shells of the goethite grains. Additional goethite occurs locally as finer-grained areas of exotic goethite. The opaque minerals in the drill core refractory ores are dominated by euhedral ilmenite crystals about 50-175 μm long. Anatase is the dominant opaque mineral in some drill core samples where it is largely pseudomorphic after ilmenite crystals. Goethite accompanies malachite in unusual drill core refractory ores that have experienced intense hydrothermal alteration. Thus, ore microscopy and petrography showed that fine-grained chalcopyrite and bornite and pre-mine malachite were not the causes of the refractory nature of the ores studied. Electron microprobe revealed that most of the copper occurred in solid solution within micas. Application of automated SEM techniques has provided a detailed understanding of the distribution of copper in these refractory ores.

Meeting Name

9th International Congress for Applied Mineralogy (2008: Sep. 8-10, Brisbane, Australia)


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Beneficiation; Carbonate Minerals; Concentration (process); Copper; Copper Compounds; Copper Deposits; Copper Mines; Core Drilling; Core Samples; Crystallography; Crystals; Drills; Hematite; Ilmenite; Iron Ores; Lithology; Mica; Microscopic Examination; Mineralogy; Mines; Mining; Open Pit Mining; Ore Deposits; Ores; Oxide Minerals; Petrography; Pyrites; Refractory Materials; Silica; Silicate Minerals; Solid Solutions; Stratigraphy; Titanium Dioxide; Titanium Oxides; Atomic Absorptions; Copper Ores; Copper Sulfides; Drill Cores; Electron Microprobe; Haematite; Hydrothermal Alterations; Open Pits; Ore Bodies; Outer Shells; Petrographic Studies; Refractory Ores; SEM Techniques; Minerals

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Document Type

Article - Conference proceedings

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© 2008 Australasian Institute of Mining and Metallurgy, All rights reserved.

Publication Date

01 Sep 2008

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