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Complete pre-cutting processes for opal doublets and triplets

Unit Descriptor This unit covers skills and knowledge to select and prepare opal and backing materials for cutting as doublets or triplets and complete all precutting processes. It includes documenting and recording all aspects of the procurement and cutting process. No licensing, legislative, regulatory or certification requirements apply to this unit at the time of endorsement.

1 . Select opal for cutting as an opal doublet or triplet.

  1. Select suitable materials for cutting as a doublet or a triplet based on market requirements and characteristics of the stone.

  2. Determine best play of colour and mark that side.

  3. Check for flaws with powerful light source and correct if necessary.

2 . Flatten opal and base.

  1. Flatten opal on marked side (this will be the best play of colour side) until surface is free of potch and impurities and completely down to the colour bar using appropriate equipment .

  2. Select backing materials and flatten.

  3. Lap opal and base until flat satin finish is obtained.

  4. Clean and dry opal and base.

3 . Cement components together.

  1. Blacken flattened surface with appropriate blacking agent .

  2. Mix adhesive to manufacturers' instructions.

  3. Ensure stone is cemented with the best colour face down.

  4. Cement flattened surfaces together eliminating excess adhesiveness and air bubbles.

  5. Allow adhesive to harden following manufacturers' instructions.

4 . Preform opal doublet.

  1. Grind stone to expose join between opal and backing.

  2. Grind stone to expose best colour.

  3. Grind to rough shape.

5 . Convert doublet to triplet.

  1. When working with a very thin opal layer, manufacture a triplet.

  2. Lap the colour surface of the opal until a thin layer of opal remains on the backing.

  3. Clean and dry stone.

  4. Cement manufactured triplet top or preferred alternative to the opal surface eliminating excess adhesive and air bubbles.

  5. After curing, grind the stone to expose both joins.

6 . Follow OHS principles when operating machinery.

  1. Follow all general OHS principles and Safe Operating Procedures when using machinery for opal cutting.

Key CompetencyExamples of ApplicationPerformance
How can information be collected, analysed and organised?
How are ideas and information communicated within this competency?
How are activities planned and organised?
How are problem solving skills applied?
How are mathematical ideas and techniques used?
How is use of technology applied?
How is team work used within this competency?

Range Statement

Suitable material may include:

Appropriate equipment may include:

Backing materials may include:

Blacking agents may include:

Adhesives may include:

Triplet top materials may include

General OHS principles and Safe Operating Procedures sheet may include:

Evidence Guide

Overview of assessment

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 select appropriate materials for making into a doublet or triplet and complete all pre-forming processes using safe working practices.

Assessment must confirm the ability to select the materials for making into a doublet and to make decisions on how to cut the material and what the final product should be. It involves preparing the opal and the backing material, flattening the stone and backing and cementing the two together. It also involves using the same skills to make a triplet from a very thin opal layer with a transparent triplet top.

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, 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, evaluation of the final product 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).

Guidance information for assessment

Assessment of this competency requires access to:

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.