1 June 2016: Anglo American is investigating possible fast-track implementation options at its Los Bronces site based on economic value identified in an extensive Grade Engineering Advanced concept study.

This article was published in CRC ORE News - June 2016

Grade Engineering at Minera San Cristobal, Bolivia

ore
  Anglo American and CRC ORE has been working jointly to redesign a new long term mine plan taking into account Grade Engineering principles.

1 June 2016: Anglo American is investigating possible fast-track implementation options at its Los Bronces site based on economic value identified in an extensive Grade Engineering Advanced concept study.

Site trials at Los Bronces have now progressed to technically validate the Grade Engineering opportunities identified in the concept study during which CRC ORE, the site team at Los Bronces and COMET Strategy worked jointly to redesign a new long term mine plan taking into account Grade Engineering principles.

CRC ORE Technical Specialists have spent significant time in Chile working with the site team and the mobile equipment operators.
Three production blast trials have been conducted. These showed that combining preferential grade by size and differential blasting improves Response Ranking numbers by 13% to 26%, noting that this result is highly dependent on underlying Ranking Responses and grade distributions. The result confirmed that grade by size is the primary value driver at Los Bronces, with differential blasting being a secondary driver. The summary outcomes of the three trials were:

  • Blast 1 was conducted in June 2015 with 33kt screened. The screening results produced a Response Ranking of 87. The minus 1 inch screened material represented 27% of the original mass, with an upgrade factor of 1.7 from the head grade.
  • Blast 2 was a differential blast which was done by only varying the charging in the high and low grade zones within the blast block. There was no change to the standard pattern design or any re-drilling conducted on the bench. Based on the screening results, the coarse low grade material had a blast P80 of ~160mm and the fine high grade material had a blast P80 of ~81mm. Results from the blast trial indicate that a good degree of separation was achieved between high grade and low grade material through differential blasting. An Overall Preferential Grade by Size Response Ranking of 80 was achieved, with an induced Response Ranking of 104 in the <1 inch material. This result indicated that the combination of natural and induced deportment provided an additional 13% to 26% improvement on the Response Ranking, dependent on the proportion of high and low grade ore across the bench.
  • Blast 3 was conducted as a “high intensity” blast assessing natural grade by size deportment. The trial assessed the impact of finer fragmentation on metal upgrading response at production scale. An overall Grade by Size Response Ranking value of 78 was achieved which provides an upgrade of 1.87 in 20% of the mass.

The pilot trials validated, at production scale, the upgrading potential of Los Bronces ores through natural and induced deportment. The trials provided Anglo American the confidence to investigate options for moving towards full-scale operational implementation.

 

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