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Elements and Performance Criteria

  1. Classify ore samples and select fluxing method
  2. Prepare for precious metal recovery
  3. Recover precious metals from ore sample
  4. Troubleshoot and correct failed recovery
  5. Perform daily maintenance of assay equipment

Required Skills

Required skills

Required skills include

planning and optimising throughput of multiple samples

accurately weighing samples and flux components

safely handling heavyhot items of equipment and hazardous chemicals

handeye coordination during pouring and knocking up buttons

recognising and identifying the cause of nonacceptable received and fused samples buttons and prills

adjusting recovery methods to solve recovery and contamination problems

Required knowledge

Required knowledge includes

chemical and physical principles relating to

fusion of mineral ores

cupellation

parting and digestion processes

expected physical and chemical properties of materials at each recovery stage

standard methods for the fire assay of a range of precious metal ores

hazards and effects of absorption of chemical reagents

control measures and operation of safety equipment

function and operation of assayequipment

enterprise andor legal traceability requirements

relevant health safety and environment requirements

Evidence Required

The Evidence Guide provides advice on assessment and must be read in conjunction with the performance criteria required skills and knowledge range statement and the Assessment Guidelines for the Training Package

Overview of assessment

Critical aspects for assessment and evidence required to demonstrate competency in this unit

Assessors should ensure that candidates can

recognise hazards and work safely at all times

interpret follow and adjust as necessary standard recovery methods

maintain close attention to technical and safety requirements in a physically demandinghazardous environment

maintain sequential control of samples through all recovery stages

optimise work flow to ensure efficiency of recovery for multiple client samples

identify indicators of poor recovery

apply a knowledge of mineral chemistry and fire assay techniques to select and implement logical corrective actions to improve recovery rates

minimise rework waste and environmental impacts

dispose of all waste responsibly

Context of and specific resources for assessment

This unit of competency is to be assessed in the workplace or simulated workplace environment

This unit of competency may be assessed with

MSLA Apply routine spectrometric techniques

MSL975020A Apply routine spectrometric techniques.

Resources may include

a variety of precious metal ore samples

fire assay methods

fire assay equipment materials and reagents

safety equipment

Method of assessment

The following assessment methods are suggested

review of quality control performance and analytical results traceable to assay samples prepared by the candidate

review of workplace documentation prepared by the candidate

feedback from peers clients and supervisors

writtenoral questioning about precious metal recovery steps typical problems and corrective actions

In all cases practical assessment should be supported by questions to assess underpinning knowledge and those aspects of competency which are difficult to assess directly

Where applicable reasonable adjustment must be made to work environments and training situations to accommodate ethnicity age gender demographics and disability

Access must be provided to appropriate learning andor assessment support when required

The language literacy and numeracy demands of assessment should not be greater than those required to undertake the unit of competency in a work like environment

This competency in practice

Industry representatives have provided the case study below to illustrate the practical application of this unit of competency and show its relevance in a workplace setting

Mineral processing

A fire pourer has noticed a large amount of fine lead shot in the bottom of a pot and seeks advice from the fire assayer The assayer examines the pot closely and notices a lime green slag colour on the inside of the pot and on the lead button Heshe identifies this as a possible chromite problem and explains that the darker the lime green colour is the higher the chromium contamination Heshe explains to the pourer that there are two ways of dealing with this problem The first is to reduce the sample weight to g for ampgt chromite or to develop its own special flux that has low litharge and silica to ensure that the sample is properly reduced Because there is no history of regular chromite problems with this particular clients samples heshe decides that a special flux is not warranted and tells the pourer to reduce the charge weight and to ensure that the components are very well mixed Heshe gives the pourer clear instructions for conducting the repeat assay and documents how the sample was treated


Range Statement

The range statement relates to the unit of competency as a whole. It allows for different work environments and situations that may affect performance. Bold italicised wording, if used in the performance criteria, is detailed below. Essential operating conditions that may be present with training and assessment (depending on the work situation, needs of the candidate, accessibility of the item, and local industry and regional contexts) may also be included.

Codes of practice

Where reference is made to industry codes of practice, and/or Australian/international standards, it is expected the latest version will be used

Standards, codes, procedures and/or enterprise requirements

Standards, codes, procedures and/or enterprise requirements may include:

Australian and international standards, such as:

AS 3988-1991 Copper, lead, zinc, gold and silver ores - Guide to sample preparation for the determination of gold

AS 3895.1-1991 Methods for the analysis of copper, lead, zinc, gold and silver ores - Determination of gold (Fire assay-Flame AAS method)

AS ISO 17025-2005 General requirements for the competence of testing and calibration laboratories

AS/NZS ISO 14000 Set:2005 Environmental management standards set

AS/NZS ISO 9000 Set:2008 Quality management systems set

calibration and maintenance schedules

enterprise recording and reporting procedures

enterprise sampling procedures for specific samples, sites and clients

environmental legislation and regulations

equipment manuals and warranties, supplier catalogues and handbooks

equipment startup, operation and shutdown procedures

industry codes of practice

material safety data sheets (MSDS)

occupational health and safety (OHS) national standards and codes of practice

principles of good laboratory practice (GLP)

production and laboratory schedules

quality manuals, training manuals and induction manuals

standard operating procedures (SOPs) and published preparation methods

Samples

Samples may include:

solids, such as rocks, minerals, soils, sands and stream sediments

core and other drill samples (rotary air blast (RAB), reverse circulation (RC) and aircore)

slurries, powder concentrates and metallurgical solutions

dump samples and grab samples

Client requests/documentation

Client requests/documentation may include:

client profile, sample identification, sample receipt, storage and analyses

required preparation method/and service charges

Assay equipment

Assay equipment may include:

mixing equipment and balances

fusion and muffle furnaces and associated spares

temperature sensors and hotplates

compressed air service, extraction systems and fuel supply lines

pots, cupels, pouring equipment, pot loader, trolleys, moulds, tongs and hammers

Hazards

Hazards may include:

dust, silica, slag, glass shards and molten flux

chemicals, such as hydrofluoric acid, bromine, perchloric acid, aqua regia, cyanide, lead-based compounds, free-mercury and nickel compounds

noise and vibration

crushing, entanglement and cuts associated with moving machinery

manual handling of heavy loads, such as pots, racks and trolleys

heat exhaustion/stress and fatigue

Safety equipment and procedures

Safety equipment and procedures may include:

ensuring access to service shut-off points, fire extinguishers/fire hose, safety shower/eye wash stations and first aid station

recognising and observing hazard warnings and safety signs

labelling of samples, reagents and hazardous materials

direct extraction and fumehoods

guards for moving machinery parts

noise insulation

using personal protective equipment, such as dust masks, heat resistant mittens, safety face shields with tinted visor, coats, ear muffs, safety boots, heat reflective clothing and latex gloves for flux handling

following established manual handling procedures

regular cleaning of equipment and work areas using enterprise procedures

reporting of abnormal emissions, discharges and airborne contaminants, such as noise, light, solids, liquids, water/waste water, gasses, smoke, vapour, fumes, odour and particulars to appropriate personnel

Fluxes

Fluxes may include:

bulk fluxes containing PbO, borax, soda ash, silica, silver nitrate and flour

non-standard flux additives:

flour (oxidising samples)

nitre (reducing samples, sulphides)

silica (basic ores)

PbO (siliceous ores)

exotic additives, such as CaF2 (refractory ores)

NiS (NiCO3, sulphur, borax and soda ash)

Pots

Pots may include:

ceramic, acidic/basic, alumina, zirconia and graphite

Sequencing of pots in a rack

Sequencing of pots in a rack may include:

addition of silver wire

addition of coloured salts (e.g. copper (Cu))

position of reagent blanks, standards, check samples

Collectors

Collectors may include:

lead (Pb), nickel sulphide (NiS), bismuth (Bi) and tin (Sn)

Criteria for an 'acceptable' button

Criteria for an 'acceptable' button could include:

one piece, mass >20g and <50g

malleable

separates cleanly from slag

free of undecomposed ore, matte and speiss

Separation of collectors

Separation of collectors may include:

cupellation

digestion

parting, annealing and weighing for a gravimetric finish

Contamination

Contamination may be caused by:

poorly made cupels

base metals (copper (Cu), nickel (Ni), zinc (Zn) and bismuth (Bi))

arsenic (As), sulphur (S), antimony (Sb), selenium (Se), tellurium (Te) and chromium (Cr)

scoria

sprouting

Documentation

Documentation may include:

pour sheets (date, time, client, pour number and preparation method)

number of pots, positions of sample, blank and check in rack

adjustments made to standard preparation methods for specific samples

analytical method

assay data

Indicators of potential loss and the corrective action

Indicators of potential loss and the corrective action may include:

viscous slag - check furnace temperature, adjust flux and lower charge weight

lead shotting - adjust flux and lower charge weight to compensate for high oxides, silicates and chromites

sulphides - adjust fusion time and adjust sample weight and/or flux

matte, speiss - adjust sample weight and flux

incomplete fusion - adjust sample weight and/or flux

unacceptable button - adjust sample weight and/or flux

inquartation - add 3 parts silver (Ag) to prill, wrap in lead foil and re-cupel

Waste

Waste may include:

rejected pots and cupels

slag and furnace material

disposable personal protective equipment

Occupational health and safety (OHS) and environmental management requirements

OHS and environmental management requirements:

all operations must comply with enterprise OHS and environmental management requirements, which may be imposed through state/territory or federal legislation - these requirements must not be compromised at any time

all operations assume the potentially hazardous nature of samples and require standard precautions to be applied

where relevant, users should access and apply current industry understanding of infection control issued by the National Health and Medical Research Council (NHMRC) and State and Territory Departments of Health