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Elements and Performance Criteria

  1. Prepare to cut an opal doublet.
  2. Cut and polish an opal doublet.
  3. Cut and polish an opal triplet (commercial top).
  4. Cut and polish an opal triplet (non commercial top).
  5. Follow OHS principles when operating opal cutting and polishing equipment.

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

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

To achieve competency in this unit a person must be able to cut and polish doublets and triplets from a range of types of opal using appropriate consumables and equipment

Assessment must confirm knowledge of the use of appropriate consumables and equipment to produce opal doublets and triplets using commercial and noncommercial triplet tops to accepted industry standards Assessment must confirm the safe completion of the cutting polishing and cleaning processes and safe use of the equipment and consumables

Competence in this unit must be assessed over a period of time in order to ensure consistency of performance over the range of variables and contexts applicable to the work environment

Context of and specific resources for assessment

This unit may be assessed in a work environment or in a simulated work environment or in a combination of these situations

Method of assessment

For valid and reliable assessment of this unit evidence should be gathered through a range of methods to indicate consistent performance

Assessment of this unit of competence will usually include observation of processes and procedures oral andor written questioning on underpinning knowledge and skills evaluation of the final product and other methods as required

Assessment methods should closely reflect workplace demands eg literacy and the needs of particular groups eg people with disabilities and people who may have literacy or numeracy difficulties such as speakers of languages other than English remote communities and those with interrupted schooling

Assessment of this competency requires access to

an opal cutting workshop

a qualified workplace assessor or assessment team


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.

Consumables may include:

cerium or tin oxide

cleaning spirit

diamond or silicon-carbide wheels #220 or #360

diamond polishing compound #2400 to #100000

diamond polishing wheels #3000 to #50000

diamond sanding wheels #280 to #1200

felt or leather buffs

personal protective equipment

silicon-carbide sanding paper #180 to #600.

Equipment may include:

grinding machinery

polishing machinery

sanding machinery

saw.

Jewellers' cutting angle requirements may include:

10º to 12º side angle (from setting edge to start of dome)

all sharp edges or acute angles be slightly rounded (optional)

flat or domed back

high overall polish and free of defects

sanded or polished back

setting edge to be straight and parallel to back

tolerance for standard millimetre sizes, 0.2mil. + or -

Wax or adhesives for dopping may include:

any 5min. adhesive, using aluminium dop-sticks

AQUADERE wood glue

hot wax sticks (hot glue gun)

super glues

vacuum dopping

wax (medium to low melting)

Note: stone should be kept cool - heat may damage opal.

Shape may include:

a variety of other shapes

cabochon

dome - high, medium, low

free form

rectangles.

Triplet top materials may include:

clear quartz

commercial standards size triplet tops

glass, plain or plate

lead crystal glass

material of the triplet top should be disclosed

synthetic spinel, corundum, topaz.

General OHS principles and Safe Operating Procedures may include:

complying with the safe operating procedures for each machine and materials

good housekeeping

using personal protection equipment where required.