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Elements and Performance Criteria

Develop knowledge of opal geology
- Identify the geological conditions suitable for the formation of opal and apply the theories of opal formation
- Determine sources of opal worldwide and locations of opal fields
Apply the principles of grading and quality assessment to opal
- 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
- Apply principles of valuing to determine the potential value of opals
Distinguish natural opal from man-made varieties
Identify and describe the different types of opal
- Identify opals of various types and describe them using correct terminology
- Develop a general awareness of types of opal treatments and determine which are acceptable in the industry

Required Skills

Required skills

communication skills to describe and document opal identification information

literacy skills to interpret information about opals

planning and organising skills to organise basic work practices

numeracy skills to apply valuation principles

technical skills to use gemmological instruments

technology skills to find information on opals

Required knowledge

sources of information on the opal industry

valuation systems for opal

functions of various opal industry sectors including mining dealing and manufacturing jewellery

accepted terminology for describing opal

safety issues associated with the use of gemmological instruments

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

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 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.

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.