Elements and Performance Criteria

The range of variables relates to the unit of competency as a whole. It allows for different work environments and situations that will affect performance.
Where reference is made to industry Codes of Practice, and/or Australian/international standards, it is expected the latest version will be used.
All operations must comply with relevant standards, appropriate procedures and/or enterprise requirements.

These procedures include or have been prepared from
Australian and international standards, such as -
AS3895.1 Methods for the analysis of copper, lead, zinc, gold and silver ores
Determination of gold (Fire Assay - Flame AAS method)
Codes of Practice (such as GLP and GMP)
material safety data sheets (MSDSs)
standard operating procedures (SOPs) and published preparation methods
quality manuals, equipment and procedures manuals
enterprise recording and reporting procedures
production and laboratory schedules.

Samples may include
solids, such as rocks, minerals, soils, sands, stream sediments
core and other drill samples (RAB, RC, aircore)
slurries, powder concentrates, metallurgical solutions
dump samples, grab samples.

Client requests/documentation may include
client profile, sample identification, sample receipt, storage, analyses
required preparation method/and service charges.

Assay equipment could include
ovens, furnaces, temperature sensors
compressed air service, extraction systems, fuel supply lines
pots, cupelles
pouring equipment, trolleys, moulds, tongs, hammers.

Hazards may include
dust, silica, slag, glass shards, molten flux
chemicals, such as hydrofluoric acid, bromine, perchloric acid, aquaregia, cyanide, lead-based compounds, free-mercury, nickel compounds
noise, vibration
crushing, entanglement, cuts associated with moving machinery
manual handling of heavy loads, such as pots, racks, trolleys
heat, exhaustion, stress, fatigue.

Safety equipment and hazard control measures may include
ensuring assess to service shut off points
recognising and observing hazard warnings and safety signs
labelling of samples, reagents and hazardous materials
direct extraction, fumehoods
guards for moving machinery parts
noise insulation
using personal protective equipment, such as mask, heat resistant mittens, boots, goggles, coats, ear muffs, safety boots, heat reflective clothing
following established manual handling procedures
regular cleaning of equipment and work areas using enterprise procedures
antidotes for specific hazards, such as hydrofluoric acid, cyanide
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 may include
bulk fluxes containing PbO, borax, soda ash, silica, silver nitrate, flour
non-standard flux additives, such as-
flour (oxidising samples)
nitre (reducing samples, sulphides)
silica (basic ores)
PbO (siliceous ores)
exotic additives, such as CaF2 (refractory ores)
NiS (NiCO 3, sulphur, borax, soda ash).
Pots may be ceramic, acidic/basic, alumina, zirconia, graphite.
Collectors may include Pb, NiS, Bi, Sn.

Criteria for an acceptable' button could include
one piece, mass >20g
malleable
separates cleanly from slag
free of undecomposed ore, matte and speiss.

Sequencing of pots in a rack could involve
addition of coloured salts (for example, Cu)
position of reagent blanks, standards, check samples.

Separation of collectors may involve
cupellation
digestion
parting and annealing.

Contamination could be caused by
base metals - Cu, Ni
arsenic, sulphur, antimony, selenium, tellurium.

Documentation could include
pour sheets - date, time, client, pour number, preparation method
number of pots, positions of sample, blank, check in rack
analytical method
assay data.

Indicators of potential loss and the corrective action include
viscous slag - check furnace temperature, adjust flux
lead shotting - adjust flux to compensate for high oxides/sulphides, add Cr, adjust fusion time
matte, speiss - adjust sample weight and/or flux
incomplete fusion - adjust fusion time, adjust sample weight and/or flux, roasting
unacceptable button - adjust sample weight and/or flux, scorification, roasting
contaminants - scorification, roasting
inquart - add Ag to prill and recupel.
Assay equipment includes the door, floor and vents of ovens; cupel furnaces, muffle liners, mixing equipment, balances, hotplates and dispensers.
Wastes include rejected pots, cupels, slag, disposable personal protective equipment.

Health, safety and environment
All operations to which this unit applies are subject to stringent health, safety and environmental (HSE) requirements, which may be imposed through State or Federal legislation, and these must not be compromised at any time. Where there is an apparent conflict between performance criteria and HSE requirements, the HSE requirements take precedence.
All operations assume the potentially hazardous nature of samples and require standard precautions to be applied. Users should access and apply current industry understanding of infection control issued by the National Health and Medical Research Council and State and Territory Departments of Health. All operations are performed in accordance with standard operating procedures.

The Evidence Guide describes the underpinning knowledge and skills that must be demonstrated to prove competence.
Critical aspects of competency

Competency must be demonstrated in the ability to perform consistently at the required standard. In particular, assessors should look to see that the candidate:

recognises hazards and works safely at all times
interprets and follows standard recovery methods
maintains close attention to technical and safety requirements in a physically demanding/hazardous environment
maintains sequential control of samples through all recovery stages
optimises work flow to ensure efficiency of recovery for multiple client samples
identifies indicators of poor recovery
selects logical corrective actions to improve recovery rates
minimises rework, waste and environmental impacts
disposes of all waste responsibly.

Underpinning knowledge

Competency includes the ability to apply and explain:

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 assay/equipment.
enterprise and/or legal traceability requirements
relevant health, safety and environment requirements.

Assessment context and methods
This unit of competency is to be assessed in the workplace or simulated workplace environment.

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
written/oral 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. Questioning techniques should suit the language and literacy levels of the candidate.

Interdependent assessment of unit

This unit of competency may be assessed with:

PMLTEST524A Apply routine spectrometric techniques.

Resource implications

Resources may include:

a variety of precious metal ore samples
fire assay methods
fire assay equipment, materials, reagents
safety equipment.

This competency in practice
Fire assay techniques are suitable for determining the concentration of gold in mineral exploration samples, particularly where a 'total' gold content is required. An assay technician is preparing a rack of samples for the day's first pour. They monitor the furnace temperature, pre-warms suitable pots and cupelles and then assembles the necessary assay equipment. They check the client specification for the first sample which is dark grey. The technician recognises that the colour indicates a high sulphide content and adds extra nitre to the flux recipe to compensate. They carefully mix the sample and flux and places the pot in the rack, carefully noting its position. The technician prepares the remaining samples, blanks and check samples according to requirements. A satisfactory fusion and pour is obtained for all samples except the sample which shows some 'lead shotting'. The technician adjusts the flux and fusion time and repeats the process. The repeat sample provides an acceptable button. They cupel the button to separate the precious metal from the collector. After parting, the prill is dissolved in a multi-acid digest and placed in a labelled container for subsequent analysis by Atomic Absorption Spectrophotometry (AAS).

The seven key competencies represent generic skills considered for effective work participation. The bracketed numbering against each of the key competencies indicates the performance level required in this unit. These are stand-alone levels and do not correspond to levels in the Australian Qualifications Framework (AQF).
Level (1) represents the competence to undertake tasks effectively
Level (2) represents the competence to manage tasks
Level (3) represents the competence to use concepts for evaluating and reshaping tasks.
Communicating ideas and information
(2)

Collecting analysing and organising information
(2)

Planning and organising activities
(2)

Working with others and in teams
(2)

Using mathematical ideas and techniques
(2)

Solving problems
(3)

Using technology
(3)