Lixiviating in Heap Leaching

In base of the picked up information from diverse sources, an estimate of costs of the U.S. Bureau of Mines (12) for lixiviating the not crushed mineral in heap leaching of 500,000 TC and recuperate the dissolved values with activated carbon, gave a value of US$ 1.14/TC processed (1978), around US$ 1.80 actual by TN; the estimate involved the construction of the floor (asphalted), carrying of the mineral, lixiviation, adsorption, desorption and regeneration of the carbon. One value pretty much superior, which can be rounded in US$ 6.00/TM, obtained Clem(4) for a hypothetic operation similar in heap leaching of 30,000 TC, where the mineral is previously crushed and aglomerated with lime or cement. In none of these estimates were the costs of mining work included.

In relation to the costs of capital, Kappes (13) has estimated in less than US$200,000 (1978) the necessary investment to iniciate an operation of 180 TPD in heap leaches of 9,000 TM with minerals without crushing, excluding the labors of the mine. As we have seen previously in the case of the plant in New Mexico (8), the total capital invested for an operation of 90 TPD, covering mining exploitation, crushing, lixiviation, adsorption with activated carbon and electro-obtaining, was of US$ 600,000 of the same year. In a recent article (1) it indicates that one operation of 2,300 TPD, in the State of Nevadam it meant an investment of US$ 10 million, and another of 6,400 TPD US$ 18 million.

An estimation of costs of lixiviation in heap leaching of minerals of gold-silver in the country, would take, nonetheless, to consider more representative examples of our reality in this sector:

In first place, one can take a handcraft work type with a few daily tons of the mineral, for example 2 or 3, where both the fracturing of the rock as the construction of the heap leaching, of some 40 to 60 TM, will be effectuated by manual means. The gold and the silver would be recuperated with activated carbon which, in its first stage, would have to be sold to the smelter to not incurr at starters in major expenses of installations. According to the data of prices compiled, the putting into movement of an operation of this nature would require between US$ 2,500 and US$ 3,000, being the items of higher meaning of the reservoirs of fiber and a chemical pump. The costs for posterior operations, supposing a time lapse of 20 days, would not exceed that of US$ 800, which in total  could reach to US$ 1,300 including mining extraction.

A common operation size in the small mining is of 50 TPD, in base of which an estimate of costs is presented in the following board. The operation supposes crushing the mineral to – ½”, alomeration with cement and lixiviation during 20 days (including loading and unloading) in a heap leaching of 1,000 TM summoned onan asphalt floor of cyclic use, requiring 5,0 kg. of cement and 1,0 kg. of NaCN by TM.