Unit of competency details

Version 

Comments 

CUVOPA201A

This version first released with CUV11 Visual Arts, Craft and Design Training Package version 1.0

Element 

Performance Criteria 

Elements describe the essential outcomes of a unit of competency.

Performance criteria describe the performance needed to demonstrate achievement of the element. Where bold italicised text is used, further information is detailed in the required skills and knowledge section and the range statement. Assessment of performance is to be consistent with the evidence guide.

1. Develop knowledge of opal geology

1.1 Identify the geological conditions suitable for the formation of opal  and apply the theories of opal formation

1.2 Determine sources of opal worldwide  and locations of opal fields 

2. Apply the principles of grading and quality assessment to opal

2.1 Identify the principles used for valuing opals in terms of base and background colours, predominant colours and patterns,  and other factors that influence an opal’s value 

2.2 Apply principles of valuing  to determine the potential value of opals

3. Distinguish natural opal from man-made varieties

3.1 Determine the gemmological characteristics  of opal based on knowledge of varieties of opal found worldwide

3.2 Select gemmological instruments  to authenticate natural opal

3.3 Use the selected instruments to authenticate opal

3.4 Identify substances used to simulate opal and synthetic opal-like substances  and compare their characteristics to natural opal

4. Identify and describe the different types of opal

4.1 Identify opals of various types  and describe them using correct terminology

4.2 Develop a general awareness of types of opal treatments  and determine which are acceptable in the industry

Overview of assessment 

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

Evidence of the ability to:

• identify and describe the characteristics of the different types of opal using correct terminology and equipment
• apply principles of valuation and determine the authenticity of opal materials.

Context of and specific resources for assessment 

Assessment must ensure access to:

• opals from various sources.

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.

Formation of opal  may include:

• opal combining with other minerals
• opal formed in:

• sedimentary deposit
• volcanic deposit (igneous)
• erratic boulders
• replacement cavities (nobbies, glauberite)
• seams
• volcanic and erosion sediments

• opal replacing:

• fossils
• wood.

Sources of opal worldwide  may include:

• Australia
• Brazil
• Hawaii
• Indonesia
• Mexico
• Slovakia
• USA.

Locations of opal fields  may include:

• New South Wales – Lightning Ridge and White Cliffs
• Queensland – various places including Winton, Quilpie, Jundah and Yowah
• South Australia – Coober Pedy, Mintabie and Andamooka.

Base and background colours  may include:

• black
• boulder – ironstone
• dark
• light.

Predominant colours and patterns  may include:

• colours, such as:

• blue
• green
• orange
• red
• violet
• yellow

• patterns, such as:

• broad
• Chinese writing
• flagstone
• harlequin
• peacock tail
• pin fire
• rolling flash
• sheen
• straw.

Other factors that influence an opal’s value  may include:

• availability of supply
• economic climate
• mining restrictions
• origin
• political situation
• rarity
• weight
• whether the sale is wholesale or retail.

Principles of valuing  may include:

• body colour
• brilliance
• inclusion and imperfections
• pattern
• play of colour
• predominant colour
• quality of cut (shape/proportions)
• shape, size and weight
• thickness of colour bar
• type.

Gemmological characteristics  may include:

• chemical composition
• colour
• fracture
• hardness
• phosphorescence
• refractive index
• specific gravity.

Gemmological instruments  may include:

• microscope
• refractometer
• S.G. scales
• standard 10X loupe
• ultraviolet lamps.

Natural opal  is classified as:

• common opal and potch
• precious opal.

Substances used to simulate opal and synthetic opal-like substances  may include:

• simulants – Gilson opal
• synthetics – for example plastics and slocum stone.

Opals of various types  may include:

• composite natural opal – doublets, triplets, mosaic and chip opals
• natural opal type 1 – opal in one piece in its natural state apart from cutting and polishing
• natural opal type 2 – opal naturally attached to the host rock – boulder opal
• natural opal type 3 – opal intimately diffused as infilling in pores or between the grains of the host rock – matrix opal
• varieties of opal:
  (N1 to N9 represents gradation from black to white in approximately 10% intervals)

• black – opal which shows a play of colour within or on a black or very dark body tone (N1, N2, N3, N4)
• dark – opal which shows a play of colour within or on a dark body tone (N5, N6)
• light – opal which shows a play of colour within or on a light body tone (N7, N8, N9).

Opal treatments: 

• may include treatments applied to improve appearance, structure or durability
• any treatment other than cutting and polishing must be disclosed.