Proactive Monitoring

Only gold and silver bars that meet our Good Delivery standards are acceptable in the settlement of a Loco London contract – where the bullion traded is physically held in London. Our proactive monitoring programme tests refiners’ competence in refining and assaying (measuring purity). If a refiner’s bars are not routinely encountered in the London vaults, they must also demonstrate their casting capabilities.

Details of a refiner’s most recent proactive monitoring activity are publicly available – see our Good Delivery Lists for details.

The testing process

We review refiners’ assaying competence on a three-yearly basis. Gold and silver refiners must undergo a supervised dip sampling process taken from a normal melt. Two of the samples are shipped to us to be check-assayed by LBMA Referees; the remainder stay on site. The refiner submits its own analysis of one sample, which is then compared with the referee’s results to determine a pass or a fail.

All gold refiners must be capable of assaying within the range of 995-999.9. Those which normally only produce four-nines gold must purchase a set of six gold reference samples from us. These samples cover the full range from 995 and above.

The refiner submits its assay results to us for comparison with the mean assay values provided by the referee. Full details of this process are explained in Annex D of the Good Delivery Rules.