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Elements and Performance Criteria

  1. Prepare to cut an opal solid
  2. Cut and polish top surface of opal
  3. Cut and polish back surface of opal
  4. Treat opal specimen

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

Evidence of the ability to

apply knowledge of the processes for cutting and polishing opals in a range of shapes

achieve a high quality finish that satisfies the requirements of the jewellery industry

Context of and specific resources for assessment

Assessment must ensure access to an opalcutting workshop with stones and equipment

Method of assessment

A range of assessment methods should be used to assess practical skills and knowledge The following examples are appropriate for this unit

observation of processes and procedures

oral andor written questioning on underpinning knowledge and skills

evaluation of the final product

review of portfolios of evidence

review of thirdparty workplace reports of onthejob performance by candidate

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

Guidance information for assessment

Holistic assessment with other units relevant to the industry sector workplace and job role is recommended

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

silicon carbide sanding paper #180 to #600

wax or adhesives for dopping.

Equipment may involve:

appropriate ventilation

grinding machinery

personal protective equipment (PPE)

polishing machinery

sanding machinery

saws.

Jewellers’ cutting angle requirements may include:

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

35º to 45º back setting edge (standard solid)

all sharp edges or acute angles to be slightly rounded

flat or domed back

high overall polish and free of defects

proportions of low, medium and high domes to be maintained

sanded or polished back

setting edge to be straight and parallel to back

thickness of stone not to exceed 2/3 of width (standard solid)

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

when leaving potch or boulder on back of stone, maintain proportions in relation to stone size, i.e. approx. 2/3 of width.

General OHS principles and safe operating procedures may include:

complying with the safe operating procedures for each machine or process

good housekeeping

using PPE where required.

Shape and dome may include:

a variety of other shapes

cabochon

dome – high, medium and low

free form

rectangles

shapes.

Treatment may include:

sugar and acid treatment

sugar and heat treatment.