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Evidence Guide: CUVOPA204A - Cut and polish solid opals

Student: __________________________________________________

Signature: _________________________________________________

Tips for gathering evidence to demonstrate your skills

The important thing to remember when gathering evidence is that the more evidence the better - that is, the more evidence you gather to demonstrate your skills, the more confident an assessor can be that you have learned the skills not just at one point in time, but are continuing to apply and develop those skills (as opposed to just learning for the test!). Furthermore, one piece of evidence that you collect will not usualy demonstrate all the required criteria for a unit of competency, whereas multiple overlapping pieces of evidence will usually do the trick!

From the Wiki University

 

CUVOPA204A - Cut and polish solid opals

What evidence can you provide to prove your understanding of each of the following citeria?

Prepare to cut an opal solid

  1. Identify and obtain consumables required for cutting an opal solid
  2. Select tools and equipment to be used
  3. Determine jewellers’ cuttingangle requirements
  4. Dop pre-form on appropriate dop stick using wax or adhesive as appropriate
  5. Follow general OHS principles and safe operating procedures when using tools, equipment, machinery and consumables for opal cutting
Identify and obtain consumables required for cutting an opal solid

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Select tools and equipment to be used

Completed
Date:

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Determine jewellers’ cuttingangle requirements

Completed
Date:

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Dop pre-form on appropriate dop stick using wax or adhesive as appropriate

Completed
Date:

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Follow general OHS principles and safe operating procedures when using tools, equipment, machinery and consumables for opal cutting

Completed
Date:

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Cut and polish top surface of opal

  1. Fine grind shape and dome ensuring continuity of contour and maintaining jewellers’ setting angles
  2. Sand opal to remove grinding marks using appropriate sanding papers or diamond wheel
  3. Polish top surface of opal with polishing compound to a high lustre
Fine grind shape and dome ensuring continuity of contour and maintaining jewellers’ setting angles

Completed
Date:

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Sand opal to remove grinding marks using appropriate sanding papers or diamond wheel

Completed
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Polish top surface of opal with polishing compound to a high lustre

Completed
Date:

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Cut and polish back surface of opal

  1. Remove stone from dop, turn over and replace on dop checking alignment
  2. Grind the back of the stone to jewellers’ standards maintaining continuity of form and alignment
  3. Sand to remove grinding marks and polish if required
  4. Remove the stone from the dop and clean the stone
Remove stone from dop, turn over and replace on dop checking alignment

Completed
Date:

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Grind the back of the stone to jewellers’ standards maintaining continuity of form and alignment

Completed
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Sand to remove grinding marks and polish if required

Completed
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Remove the stone from the dop and clean the stone

Completed
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Treat opal specimen

  1. Select opal specimen for treatment and check to ensure it will benefit from treatment
  2. Grind, sand and polish selected area
  3. Treat the selected area
  4. Clean or neutralise as required
Select opal specimen for treatment and check to ensure it will benefit from treatment

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Grind, sand and polish selected area

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Treat the selected area

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Clean or neutralise as required

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Assessed

Teacher: ___________________________________ Date: _________

Signature: ________________________________________________

Comments:

 

 

 

 

 

 

 

 

Instructions to Assessors

Evidence Guide

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 opal-cutting 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 and/or written questioning on underpinning knowledge and skills

evaluation of the final product

review of portfolios of evidence

review of third-party workplace reports of on-the-job performance by candidate.

Assessment methods should closely reflect workplace demands (e.g. literacy) and the needs of particular groups (e.g. 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.

Required Skills and Knowledge

Required skills

planning and organising skills to plan work logically

problem-solving skills to identify and address common cutting and polishing problems

numeracy skills to use numerical features of machinery

technical skills to cut and polish opals using correct technique.

Required knowledge

characteristics of opal gemstone structure

processes and consumables needed for cutting and polishing opals

safety issues associated with opal cutting and polishing machinery.

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.