Application
This unit requires the application of knowledge and skills to identify and apply valuing principles to different types of opal based on sound understanding of how opal is formed, where it is found and the characteristics of the gemstones. The work is done in line with industry practice and may be applied in a range of environments from cutting and polishing to retailing, wholesaling, selling on the Internet or mining. 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. |
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. |
Elements and Performance Criteria
ELEMENT | PERFORMANCE CRITERIA |
1 Develop knowledge of opal geology. | 1.1 Identify the geological conditions suitable for the formationof opal and explain the theories of opal formation. 1.2 Determine sources of opal worldwide and locations of opal fields in Australia. |
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 the predominant colours and patterns 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 thegemmological 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 using correct opal nomenclature and terminology. | 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. |
Required Skills
Required skills: communication skills to describe and document identification information basic research skills skills in using gemmological equipment. |
Required knowledge: industry sources of information valuation systems functions of various industry sectors, for example mining dealing, manufacturing jewellery etc accepted terminology. |
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. | |
Critical aspects for assessment and evidence required to demonstrate competency in this unit | Assessment must confirm accurate identification and description of the characteristics of the different types of opal using correct terminology and equipment in a variety of work environments, and the ability to apply principles of valuation and determine the authenticity of opal materials. |
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 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. |
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 a sedimentary deposit opal formed in a volcanic deposit (Igneous) opal formed in erratic boulders opal formed in replacement cavities (nobbies, glauberite xls.) opal formed in seams opal formed in volcanic and erosion sediments opal replacing fossils opal replacing wood. |
Sources of opal worldwide may include: | Australia Brazil Hawaii Indonesia Mexico Slovakia USA. |
Locations of opal fields in Australia may include: | New South Wales - Lightning Ridge, White Cliffs Queensland - various places including Winton, Quilpie, Jundah, Yowah South Australia - Coober Pedy, Mintabie, Andamooka. |
Base and background colours may include: | black boulder - ironstone dark light. |
Predominant colours and patterns may include: | colours such as but not limited to: blue green orange red violet yellow |
patterns such as but not limited to: 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/imperfections pattern play of colour predominant colour quality of cut (shape/proportions) shape size/weight thickness of colour bar type. |
The 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 also the naked eye gives a good judgment. |
Natural opal is classified as: | common opal and potch - opal which does not exhibit a play of colour precious opal - exhibiting a play of colour. |
Substances used to simulate opal and synthetic opal-like substances may include: | simulants - Gilson opal synthetics - for example plastics; 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: 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 Note: Any treatment other than cutting and polishing must be disclosed. |
Sectors
Not Applicable
Competency Field
Opal cutting and polishing | |
Employability Skills
This unit contains employability skills. |
Licensing Information
Refer to Unit Descriptor