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This paper compares the behavior of gold and ore in the grinding circuit of Hemlo Mines Ltd. Particular attention is given to grinding kinetics, classification behavior and liberation. For grinding kinetics, laboratory grinding of gold flakes and silica, 840 um to 1200 um in size (14/120 mesh), was also performed to provide a standard for comparison and to study in a controlled environment the mechanisms of breakage, folding, smearing and impacting. Grinding kinetics were characterized at laboratory scale with breakage and selection functions. The breakage function showed that 75% of gold disappearing from the 840 um to 1200 um class reported to the 600 um to 840 um; this figure is much higher than for silica (46%) or most other minerals and implies that comparatively fewer fine fragments are produced from the breakage of gold flakes on account of gold’s malleability. The selection function of silica was four times that of gold. At plant scale, the ratio of the selection function of ore and gold increased from 6 for at 50 um to 100 um to 20 at 500 um to 1000 um. Observation of original flakes and their fragments with the scanning electron microscope showed that the main mechanism of “grinding” from the 840 um to 1200 um to the 600 um to 840 um class was folding rather than actual breakage. This was confirmed by a measure of individual flake weight. The postulated breakage cycle is that relatively globular flakes become increasingly serrated through grinding; they can then regain their original shape.

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		KMPC Hemmat A Mineral Processing Digital Library
	All Years to Access Full-Text Export citations The behaiour of gold in Hemlo Mines Ltd. grinding circuit By S. Banisi, A.R. Laplante and J. Marois Published in CIM Bulletin, Vol. 84, No. 955, 1991 at 1991 Direct link: http://kmpchemmat.ir/pii/30566 Abstract This paper compares the behavior of gold and ore in the grinding circuit of Hemlo Mines Ltd. Particular attention is given to grinding kinetics, classification behavior and liberation. For grinding kinetics, laboratory grinding of gold flakes and silica, 840 um to 1200 um in size (14/120 mesh), was also performed to provide a standard for comparison and to study in a controlled environment the mechanisms of breakage, folding, smearing and impacting. Grinding kinetics were characterized at laboratory scale with breakage and selection functions. The breakage function showed that 75% of gold disappearing from the 840 um to 1200 um class reported to the 600 um to 840 um; this figure is much higher than for silica (46%) or most other minerals and implies that comparatively fewer fine fragments are produced from the breakage of gold flakes on account of gold’s malleability. The selection function of silica was four times that of gold. At plant scale, the ratio of the selection function of ore and gold increased from 6 for at 50 um to 100 um to 20 at 500 um to 1000 um. Observation of original flakes and their fragments with the scanning electron microscope showed that the main mechanism of “grinding” from the 840 um to 1200 um to the 600 um to 840 um class was folding rather than actual breakage. This was confirmed by a measure of individual flake weight. The postulated breakage cycle is that relatively globular flakes become increasingly serrated through grinding; they can then regain their original shape.