Diliman, Quezon City - The Metallurgical Technology Division of the Mines and Geosciences Bureau is conducting a technical study on the recovery of residual gold from tailings of small-scale mining operations. This two-year project is aimed to generate various schemes of gold recovery processes with corresponding capital and operating cost estimates to treat various types of gold mill tailings.

Residual gold in tailings from small scale operations may come in different forms and assays due to crude or unoptimized methods such as poor grinding and incorrect leaching. Tailings from gravity concentration and/or amalgamation may still contain significant gold due to coarse grind while those coming from cyanidation process may contain gold locked in sulphides and/or also due to coarse grind.
 
The target sampling sites for the project are the provinces of Agusan del Sur, Camarines Norte, and Compostela Valley. Tailings samples from these areas will undergo microscopic and analytical tests to determine gold morphology/occurrence and content.  Also, interviews with the tailings owners or former processors will also be conducted to verify the method and extent of gold recovery process employed.  The information from these activities will be vital in selecting the gold recovery scheme to be tested in the laboratory. It is envisioned that pre-leaching steps such gravity concentration, flotation and roasting will be experimented on prior to standard cyanidation, carbon adsorption and possible detoxification tests. 

It is most likely that processing of mill tailings is less expensive because the materials are already in ground form unlike the raw ores which need to be crushed and ground.  In a typical mineral processing operation of fresh ore, 60% of power consumption is attributed to size reduction process (i.e., crushing and grinding). Although re-grinding may be employed in this research to liberate the gold in coarse tailings, this will just be conducted to the gravity or flotation concentrates.

This said project is aligned with RA No. 7076, otherwise known as the “People’s Small-Scale Mining Act of 1991” and Executive Order 79 which mandate concerned government agencies to come up with measures to improve and address issues on small-scale mining activities.

 

By: Metallurgical Technology Division

 

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