Escudo de la República de Colombia

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Procedure to detect gold and silver patented

In just 4 days it is now possible to determine the auriferous and argentiferous potential of deposits thanks to a procedure designed and patented by the Universidad Nacional de Colombia (UNal) in Medellín.

Medellín, 17 de marzo de 2016Agencia de Noticias UN-

Gold exploitation needs new technologies.

In 2015 gold production reached 1,903,386 million troy ounces, a 3.84% increase with respect to 2014.

Native gold which is found mainly in alluviums tends to produce mistakes in quantification of this metal, process known as the nugget effect.

Cimex methodology enables reducing up to 70% of the workforce and analysis times, reducing it from 15 to 4 days.

Moisés Bustamante Rúa, Cimex Researcher.

Researchers of the Faculty of Mining’ Minerals Institute (Cimex, for its Spanish acronym) Ana Cecilia Gaviria Cartagena (R.I.P.), Óscar Jaime Restrepo Baena and Moisés Oswaldo Bustamante Rúa, designed an innovative procedure for determination of precious metals through mineral samples tested in the lab. 

Despite being an activity which produces revenue to the country, exploitation of this resource does not have the technology to achieve greater efficiency and environmental sustenance. Additionally innovation is not encouraged in the industrial gold production chain. 

This situation is also present when exploring the auriferous potential of a deposit and assessing reserves. For this, they traditionally produce a method where geological models and geologists and mining engineers expertise are combined with previous evidence, for instance in a paleobasin (former riverbed) or aquifer vein. 

Therefore, “They map the land and establish possible testing areas through perforation. This is carried out without having the certainty that the result will be positive,” said Bustamante. 

When the sample is sent to the laboratory it is prepared using a standardized protocol. Then, thanks to a physical or gravitational strategy, native gold is isolated. Afterwards using a pyrometallurgical method (high temperature to melt the sample) they separate gold from silver. Lastly they carry out a hydrometallurgical procedure and extract, purify and recover the precious metal. 

Since the earth’s crust is so variable, gold and silver is not always accompanied by the same minerals. Therefore and not considering the classic laboratory procedures, which handle samples in the same manner, researchers use different types of preparations according to the ore. 

In other words, says Bustamante, if a sample arrives with sulphur it is prepared in a certain manner or if it has graphite it is prepared differently. Therefore the protocol devised allows for selective treatment according to the minerals in the ore, avoiding quantification mistakes. 

Therefore Cimex methodology enables reducing up to 70% of the workforce and analysis times, reducing it from 15 to 4 days. Furthermore statistical mistakes do not surpass 3% of most cases and diminish mistakes in finesse valuations (measure which describes concentration of precious minerals) in auriferous and argentiferous minerals. 

The nugget effect 

Gold essentially has two origins according to the deposits. One is from alluvium deposits, like when materials have been carried by rivers or surface water and the other comes from crystallized minerals in rocky masses which have not suffered alterations or metamorphisms and therefore are imbedded in seams or veins. 

To determine the metal, according to the source and deposit genesis, it is possible to discover free or native gold and other types of aquifer ores linked to sulphur. 

Native gold which is found mainly in alluviums tends to produce mistakes in quantification of this metal, process known as the nugget effect. To try to overcome this issue, traditionally they increase the amount of samples, which is more expensive, as this requires a logistical strategy, use of regents and more energy. 

For Bustamante this new technique will enable not only specifying the areas where gold and silver deposits are, by measuring the nugget effect, but also hopes legal firms will carry out greater efforts to extract lost gold. In this manner, perhaps they could avoid granting more mining licenses.

(Por: Fin/DG/DMH/APBL
)
N.° 317

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