Manus investigates new cyanide leaching technology

New leaching and electrowinning technology could be the key to profitability at the Sullivan project in Nevada.

Consolidated Manus Industries (VSE) can acquire the property by making a final payment of US$1.13 million on or before April 25 (an extension from the original deadline of Feb. 24). An initial payment of US$400,000 was made last year.

John Chapman, newly appointed chairman of Manus, says the technology employs cyanide to leach both copper and gold, followed by precipitation and electrowinning to produce both metals.

The project hosts an potentially open-pit resource of 12.7 million tons grading 0.027 oz. gold per ton and 0.34% copper, based on 1991 estimates. (A previous study, in 1982, estimated the resource at 10.2 million tons grading 0.039 oz. gold and 0.37% copper.)

Chapman points out that, were only one metal to be recovered, the project would probably not be economic; hence the necessity of a technology that allows for the recovery of both copper and gold simultaneously. Key to the new technology is the use of an organic reagent to remove and concentrate the gold and copper, as well as the use of a membrane in the electrowinning process.

After conventional cyanide leaching, copper and gold in the weak pregnant solution are selectively extracted using an organic-based reagent. The reagent is then stripped into a strong pregnant solution and the gold is selectively precipitated on to copper scrap, shot or powder. The resulting sludge can be refined into gold bullion.

The remaining pregnant solution, now stripped of gold, is advanced to an electrolytic cell where the copper can be electrowon on to stainless steel cathodes. The electrowinning technology will use membraned cells to prevent the cyanide solution from coming into immediate contact with the anode. (The anode produces oxygen, which destroys cyanide complexes. The recirculation of the cyanide is an important factor in project economics.)

It is believed that a similar process is being patented by DuPont. Research into the new method was carried out under the supervision of Dr. David Dreisinger at the University of British Columbia, while funding was provided jointly by Placer Dome and a numbered company in British Columbia. Chapman is a principal and a major shareholder of the latter, along with Frederick Sveinson who also joined the board of Consolidated Manus. The numbered company provides Consolidated Manus with funding for the initial option payment on the Sullivan property, as well as US$150,000 for metallurgical work related to the deposit. The loan takes the form of a $850,000 debenture which bears no interest and which is convertible into units of Consolidated Manus at 50 cents each. The units consist of one share and one warrant exercisable at 65 cents to March 17, 1996, and 75 cents to March 17, 1997.

Consolidated Manus has 6.1 million shares outstanding and is raising funds to cover the final payment on the Sullivan property.