Opal
Opal has been attributed with various qualities over the years, from bringing misfortune and hardship to the wearer to possessing therapeutic properties for diseases of the eye. However accurate these associations may be, one fact remains true: opal might be easy to damage and demanding to work with, but it is impossible not to be seduced by its sheer celebration of colour.
The vibrant colours that appear on an opal result from the diffraction of light off tiny, closely packed silica spheres inside the stone. This is why the colours change when the opal is viewed from a different direction. The larger and more ordered these spheres are, the greater the range and intensity of colours produced. This interference of light is called colour play or iridescence. The term opalescence shouldn't be used to describe opals, as it actually refers to the bluish white shimmer, or schiller, on gemstones such as moonstone.
While most gemstones are cut, or faceted, to calibrated sizes and shapes, opals are frequently cut as cabochons with freeform shapes. This is accepted practice and simply a result of the cutter wanting to maximize the opal and the colour play found on the rough material. The irregular shapes make each opal unique and the stones often bring creativity to jewelry design.
Opals in jewelry
jewelry makers of the Art Nouveau period rebelled against the conventional forms of the late Victorian era and began producing "organic" pieces that contained inexpensive, colourful cabochons. Opals were used extensively; they fitted in perfectly with the insect motifs and their colour play matched the beautiful enamel work. They proved to be a versatile and popular gemstone.
An opal is everything that a diamond is not, yet they make a winning combination. The brilliance and fire of small faceted diamonds complement the more subtle colour play of the opal cabochon. The diamonds also form a protective barrier around the opal, receiving (and surviving) any accidental impact while the fragile opal remains undamaged.
Traditionally, fire opal has been cut into faceted beads and strung in graduated colours. It is now possible to find other types of opal in bead form, including precious opal (black and white), boulder opal and Andean opal, as well as cheaper varieties of common opal.
Treatments and imitations
- Opal doublets and triplets are synthetic composite opals. In a doublet, the top section of the stone is precious opal, but the base is common potch opal. A triplet has three layers: a base of common opal, a thin middle layer of precious opal and a protective top dome of rock crystal. These stones are easy to spot if you look at them side-on through a loupe.
- Imitation Gilson opals were developed in the laboratory in 1973. They had a good iridescence, but the patterning of colour identified them as imitations.
- In the United States, John Slocum developed opals made of tough glass. They lacked the texture of genuine opal and appeared crumpled under magnification.
- Polystyrene latex opal beads and stones are widely available. They have a milky bluish sheen that can be spotted easily.
Opals are all about colour: the better and more even the colour, the higher the value of the opal. To assess evenness of the colour play, rotate the opal through 360 degrees. A good stone should have colour spread across the entire surface with no "dead" patches.
The most expensive colour of opal is red. Yellow, green and blue are more common colours and so cost slightly less.
Working with opal
- When designing your piece of opal jewelry, it is vital that you the type of background the stone will have. Check the colour poi of your opal and decide on the effect you want. Different colours of metal will boost different colours in a stone and the setting will affect the strength of the iridescence.
- When designing the piece of jewelry and setting the stone, keep in mind that opal is quite a soft stone and is easily damaged by pressure and impact. If opal is being used for a ring, a rub-over setting will protect it whereas a claw setting will expose the stone's edges and leave it vulnerable to damage. The softness of opal makes it suitable for carving, but care needs to be taken as it is quite brittle.
- If you plan to work on the opal using dui attachments there is a risk that any heat generated will evaporate the opal's water content, causing dehydration, cracking and a loss of colour play. Sometimes it is possible to restore the water content of the damaged opal by immersing it in water. Evaporation of water content happens naturally over time and can be avoided by storing the opal in moist cotton wool.
- Opal is sensitive to acids and alkalis. Its porous nature makes it vulnerable to perfumes, soaps and detergents, so jewelry should always be removed before washing or applying creams
Andean opal
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
Created: 04-10-2009 04:35:34
Modified: 04-10-2009 04:35:34
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
Created: 01-01-1970 10:00:00
Modified: 01-01-1970 10:00:00
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