Assessor Resource

CUVOPA04B
Cut and polish an opal solid

Assessment tool

Version 1.0
Issue Date: April 2024


The skills and knowledge covered by this unit are applied in a workshop environment and include all phases of the process for cutting a variety of opal shapes to accepted industry standards and the safe use of the equipment.

Where appropriate the outcomes of this unit could be contextualised to apply to other gemstones. Examples of aspects of the unit that may need to be adjusted would include:

the specific properties of each gemstones

industry and market requirements

underpinning knowledge

Range Statement.

This unit covers skills and knowledge required to cut and polish an opal solid to make a finished cabochon or other shapes from a preformed stone.

No licensing, legislative, regulatory or certification requirements apply to this unit at the time of endorsement.

You may want to include more information here about the target group and the purpose of the assessments (eg formative, summative, recognition)

Prerequisites

This unit may be assessed on its own or it may be assessed with other units that cover related skills and knowledge.

Evidence is most relevant when provided through an integrated activity which combines the Elements of competency for the unit, or a cluster of units of competency.

Employability Skills

This unit contains employability skills.



Evidence Required

List the assessment methods to be used and the context and resources required for assessment. Copy and paste the relevant sections from the evidence guide below and then re-write these in plain English.

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

Assessment must confirm knowledge of the processes for cutting and polishing opals in a range of shapes and the skills to achieve a high quality finish that satisfies the requirements of the jewellery industry.

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 and/or written questioning on underpinning knowledge and skills and other methods as required.

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).

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.

Assessment of this competency requires access to:

an opal cutting workshop

a qualified workplace assessor or assessment team.

Submission Requirements

List each assessment task's title, type (eg project, observation/demonstration, essay, assingnment, checklist) and due date here

Assessment task 1: [title]      Due date:

(add new lines for each of the assessment tasks)

Assessment Tasks

Copy and paste from the following data to produce each assessment task. Write these in plain English and spell out how, when and where the task is to be carried out, under what conditions, and what resources are needed. Include guidelines about how well the candidate has to perform a task for it to be judged satisfactory.

Required skills:

use of appropriate equipment

ability to select the appropriate consumables.

Required knowledge:

characteristics of opal gemstone structure

processes and consumables needed for cutting and polishing opals.

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

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 be slightly rounded (optional)

flat or domed back

high overall polish and free of defects

proportions of low, medium and high domes 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.

Dop may include:

hot or cold dopping

Note: cold dopping is preferred as hot dopping may damage the opal and cold dopping is preferable for long term stability.

Shape and dome may include:

a variety of other shapes

cabochon

dome - high, medium, low

free form

rectangles

shapes.

Treatment may include:

Sugar and acid treatment or sugar and heat treatment for Andamooka matrix (other treatments are used but are not acceptable in the industry)

Note: if opal is treated or in any way altered other than cutting and polishing, the treatment must be disclosed to prospective buyers.

General OHS principles and Safe Operating Procedures may include:

complying with the safe operating procedures for each machine or process

good housekeeping

using personal protection equipment where required.

Copy and paste from the following performance criteria to create an observation checklist for each task. When you have finished writing your assessment tool every one of these must have been addressed, preferably several times in a variety of contexts. To ensure this occurs download the assessment matrix for the unit; enter each assessment task as a column header and place check marks against each performance criteria that task addresses.

Observation Checklist

Tasks to be observed according to workplace/college/TAFE policy and procedures, relevant legislation and Codes of Practice Yes No Comments/feedback
Identify and obtain consumables required for cutting an opal solid. 
Select tools, and equipment to be used. 
Determine jewellers' cutting angle requirements. 
Dop preform on appropriate dop stick using wax or adhesive as appropriate. 
Fine grind shape and dome ensuring continuity of contour and maintaining jewellers setting angles. 
Sand opal to remove grinding marks using appropriate sanding papers or diamond wheel. 
Polish top surface of opal with polishing compound to a high lustre. 
Remove stone from dop, turn over and replace on dop checking alignment. 
Grind the back of the stone to jewellers' standards maintaining continuity of form and alignment. 
Sand to remove grinding marks and polish if required. 
Remove the stone from the dop and clean. 
Select opal specimen for treatment and check to ensure it will benefit from treatment. 
Grind sand and polish selected area. 
Treat the selected area. 
Clean or neutralise as required. 
Follow all general OHS principles and Safe Operating Procedures when using tools, equipment, machinery and consumables for opal cutting. 

Forms

Assessment Cover Sheet

CUVOPA04B - Cut and polish an opal solid
Assessment task 1: [title]

Student name:

Student ID:

I declare that the assessment tasks submitted for this unit are my own work.

Student signature:

Result: Competent Not yet competent

Feedback to student

 

 

 

 

 

 

 

 

Assessor name:

Signature:

Date:

Assessment Record Sheet

CUVOPA04B - Cut and polish an opal solid

Student name:

Student ID:

Assessment task 1: [title] Result: Competent Not yet competent

(add lines for each task)

Feedback to student:

 

 

 

 

 

 

 

 

Overall assessment result: Competent Not yet competent

Assessor name:

Signature:

Date:

Student signature:

Date: