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
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.
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. |
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