SPOTLIGHTon the Accounting for Gold School

The School on the Accounting for Gold, which wasorganized under the auspices of The South AfricanInstitute of Mining and Metallurgy by Dr Hugh E. Bart-lett, Consulting Metallurgist of Johannesburg Consoli-dated Investment Company Limited, was held at theSouth African Nature Conservation Centre at Delta Park,Johannesburg, on 15th to 17th May, 1989. It was attend-ed by 178 delegates, including 2 from the OK and 4 fromZimbabwe. A total of 19 papers were presented coveringthe components of gold-accounting procedure, samplingtechniques, and new sampling technology.

Mr Gene Fivaz, President of the Institute, in his open-ing address, emphasized the importance of containingproduction costs in order to maintain the Republic's com-petitive position in world markets. In respect of thecountry's gold-mining industry, he stressed the need foraccuracy in the measurement of both tonnages and valuesto provide management with the confidence required forcorrective action to ensure the maintenance of profit-ability.

Technical ProceedingsOn the first day, after an overview and a discourse on

statistical concepts and sampling theory by Dr Bartlett,the papers dealt with the basics of underground andsurface ore accounting, and analyses of undergroundsampling techniques from chip sampling to the double-bladed diamond saw and broken-ore sampling.

The second day started with a series of papers by DrBartlett dealing with the difficulties of run-of-minesampling, the need for statistical testwork in the designof run-of-mine sampling systems, the measurement ofmass on gold mines, and mechanical sampling in plants.He laid emphasis on the advantages to be gained fromthe sampling of feed to the mills and, when ore originatedfrom a variety of sources, from the sampling of feed fromthe different sources. He also described the practice andstrategies of stop-belt sampling in some detail. Of par-ticular interest was the 'revolutionary' go-belt samplerdesigned by JCI engineers.

Papers dealing with sampling and evaluation procedureswithin the Rand Refinery, and with the measuring andmonitoring of analytical performance, were most illu-minating. The day was capped by a description of Aztec,which is an automatic gold-ore analyser for use in assayoffices, and of the long-heralded and equally long-awaitedunderground gold analyser.

The first paper of the third day dealt with a practicalhopper-sampling technique that is used as an early-warning system of grade problems. This was followed bymore-academic papers, of particular interest being a

.Assistant Consulting Engineer, Gold Fields of South Africa Limited,75 Fox Street, 2001 Johannesburg.

182 JUNE 1989 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

by D.L. MORRISON*

paper on the smoothing of material balances. This is astatistical tool for the adjustment of assay and flowratedata in an effort to produce consistent material balances.

The final paper described gold accounting from theface to the final product at a large gold mine, and intro-duced a system for the sub-division of the mine call fac-tor into a shaft call factor, a tram call factor, and a plantcall factor, each dealing with a relevant section of the mn-of-mine ore flow. The practice of stop-belt sampling isapplied extensively in determining the components of thevarious factors. The claims made of improved profitabili-ty arising from these intensive monitoring procedureswere most impressive.

A panel discussion after lunch in respect of the minecall factor was chaired by Mr Peter Kraus, recently retiredGroup Surveyor of Anglo American. The discussion waslively, and gave rise to the following major conclusionsand comments.

(i) Sweepings and accumulations of ore left under-ground are significant components of a poor minecall factor.

(ii) Extrapolation from sample value to block value isa considerable problem, and the reliability of theestimation depends on truly representative sampling.In this respect, it was claimed that a controlled chipsample will match a diamond-saw sample.

(iii) In response to criticism that gold estimation requiresgeological (specifically sedimentological) input, theChairman explained that all the mining houses makeuse of geological/survey valuation teams.

(iv) Dr Bartlett outlined the major valuation controlpoints, and stressed that stop- or go-belt samplingof the belt between shaft and plan is the key para-meter.

(v) Gold loss to residues is insignificant, since themeasuring and sampling facilities available enablemanagement to exercise adquate control.

(vi) Gold theft continues in handfuls or shopping-bagamounts, but is significant only in breaking-and-entering operations.

The discussion had to be cut short at this stage owingto lack of time, and Dr Bartlett officially closed theschool.

AcknowledgementsThe Institute acknowledges the sponsors of the various

exhibition stands, particularly Ramsey Engineering, whosponsored a superb barbecue at the end of the first day.

The Institute itself is to be congratulated for arranginga most interesting and extremely useful seminar.

PhotographsThe captions of the accompanying photographs, which

were taken by Carlos Dias, all read from left to right.

Gene Fivaz (President, SAIMM)and Peter van Rensburg (Lin-

dum Reefs)

Carl Neveling (Chromatech In-struments), Colin Tite (MetrandManagement Services), Mal-colm Prosser (Vaal Reefs), andChris Sharland (Interlect In-

struments, UK)

Johan Heunis (JCI), Clive Hunt(CA Consultants), and Hugh

Bartlett (JCI)

JUNE 1989 183JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

Pieter van Aswegen, ColinPask, Johan van Walsen, andAndy Carter (all of Genmin)

Arthur Roberts (Doornfontein),and Neville Paterson and Don

Ross-Watt (Gold Fields)

Abe Rozendaal (West Driefon-tein), Peter Camden-Smith(Rand Mines), and Phil Lam-

bert (Northam Platinum)

184 JUNE 1989 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

Christopher Sanderson (GoldFields), Trevor Gillard (Bly-vooruitzicht), and Michael

Botha (East Driefontein)

Philip Stark (Freegold South),and Richard Thompson andJeremy Mann (Western Deep

Levels)

Andrew King (West Driefon-tein), Stuart Saich (Doornfon-tein), and Pieter Coetzee (West

Driefontein)

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY JUNE 1989 185

Flip Zietsman (Blyvooruitzicht),Tim van Zeller (Harmony), and

Roy Dias (Rand Mines)

George Perry (Harmony), Jim-my Hockly (Rand Mines), andPeter Kucharski (Blyvooruit-

zicht)

Ralph English (JCI) and JohnFreer (Genmin)

186 JUNE 1989 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY