Processing and Upgrading

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Terra Resources aims to obtain products with commercial value from slag, one of the more important waste generated during pyrometallurgical copper extraction. This waste contains interesting amounts of compounds with an important commercial value. The objective of this work is to identify the best-oriented process to obtain commercial products, considering slag as a new ‘mining resource’ with chemical and physical properties different from the original copper ores. The products or by-products to obtain are basically: copper, silica, iron oxides, precious metals and some others minor products reported by smelter plants.


Terra Resources owns and has access to millions of tons of secondary material across its asset base. Initial estimates indicate an extensive, but poorly explored resource background of Non-Ferrous Metals, including Copper, Lead and Zinc with varying but high degrees of contained Precious Metals which offers a great opportunity to reclaim scalable base and precious metals concentrate.


Secondary material is transported to our processing facility by truck to be processed in the next stage of the value chain.

Crush and Mill

During the course of beneficiating secondary material to concentrate, the objective is to produce an economically viable concentrate via crushing in our ball mill. A mesh screen resends coarse material for grinding.

Gravimetric Separation

Secondary material is processed for the purpose of producing a highly valuable and marketable concentrate which carries high levels of copper and other non-ferrous metals, with contained precious metals content.

Since, iron oxides and silica compose the slag, a good response to gravimetric and magnetic treatment is expected. If optimized, a separation between higher and lower density compounds yield two concentrates. That means precious metals, copper and part of iron oxides in one side, the rest of iron oxides, silica and others light compounds on the other.


Sampling and assaying is the next step in the processing flow, prior to the treatment of the incoming material and the subsequent refining of the recovered metals. Determining the exact metal content of the supplied materials is essential as it forms the contractual basis for metal value payment.


Newly produced non ferrous gravimetric concentrate is bagged, sampled and sent to our customers worldwide that range from traders to smelters.

Extracting Value from Secondary Material

The difficulty in processing the secondary material is directly linked to the association of the copper values with other metals and compounds present in the secondary material. Therefore gravitational separation has been identified as the most economical option to recover copper and precious metals from low-grade secondary material which represents significant economic potential given the vast quantities under ownership.
Characterisation of material
The most important characteristic of material is its chemical content. This characteristic determines if the material in question could be economically processed and what technology should be applied for its processing. Chemical content of Romplumb secondary material from integral samples is given in Table 1. As it can be seen the contents of copper, silver and gold are 1.47 %, 1708 g/t and 59.6 g/t, respectively.

The secondary material contains a considerable amount of basic useful components, copper, gold and silver. In order to find a technology for its economically justified and ecologically acceptable processing, a large number of experiments were conducted. Copper gravitational separation from the material showed that it is possible to recover 80 % of copper utilising this process. 


As while as gravitational separation is concerned, both chemical and mineral contents, were signifying that good recovery results could be expected. Results of laboratory testing show that by optimising gravitational separation techniques process and choosing appropriate reagents, recovery of copper is approximately 90 % along with copper content in basic copper concentrate of 15 %. In addition, a properly chemically-induced plant provides precious metal upgrading for levels suitable for the market. 

Sample 1

Copper (%)
Silver (g/t)
Gold (g/t)




Sample 2

Copper (%)
Silver (g/t)
Gold (g/t)




Sample 3

Copper (%)
Silver (g/t)
Gold (g/t)




Sample 4

Copper (%)
Silver (g/t)
Gold (g/t)




Samples Carried out by SGS and Alfred Knight