Contraluzopal ~ Bruce Maher introduction to contra luz opals
ContraluzopalIntroduction to contra luz opals |
| Opal, the queen of gems, in its most precious form shows the brilliant spectral shifting colors that make it among the most prized of natural substances. Known from antiquity (Pliny the Elder mentions it in his Roman histories as the cause of a blood feud among the aristocracy over a choice piece known as "the burning of Troy") opal has come in and out of fashion generation by generation. An unsavory reputation was acquired in the early 19th century as a result of a gothic potboiler by Sir Walter Scott in which an ill-omened stone was stolen from the eye of a Hindu idol destroys all who come into its possession. This reputation was enhanced by the presence of Hungarian opal jewelry in the booty of the bloodbath of the Crimean War. Queen Victoria, anxious to popularize a resource of her Australian colony, began including opals in her military honors. Whatever the cause, by the turn of the century opals had become the symbol of both the fashionable times and the quintessence of femininity. While the Belle Epoch jewelers continued to produce heavily diamond encrusted status symbols, a new generation of Bijoutiers concentrated on small works of art distinguished by using component materials for their effect more than their intrinsic value. Paradoxically, opal values shot up as masters such as Rene Lallique flourished. The 1st World War and Great Depression periods saw opals as fussy and old fashioned, but the Deco period saw another resurgence. Just as they began to fade away, along came World War II and thanks to the U.S. Army another generation of fans. In order to occupy their spare time, the army began a program of teaching arts and crafts and 'shop' to the enlisted men -- one of the most popular was lapidary. The local PX frequently stocked heavily discounted and subsidized gem rough. Among the most popular cabbing material was Australian and Mexican opal nodules. A whole generation of rockhounds and societies resulted. Just as this group began to fade, we get the 60's. Can you tangibly define psychedelic better than opal? |
| Found worldwide, only a tiny percentage is precious. Each location is idiosyncratic, with different base colors characteristic of different regions. Australia is the primary source and known for its whites, blacks, boulder, and jelly. Mexico and Oregon material are similar, mostly jelly in water clear to white and yellow through Nehi orange found in Rhyolite matrix, primary sources for contra-luz. Brazil produces slightly harder precious white opal and much common fire opal for faceting, usually hazy yellow to light orange, often large. Honduras Guatemala Peru -- common blue opal -- some greenish, usually seen as beads. |
| Stability, or rather instability, is a critical consideration. Many mines produce material that cracks upon exposure. While this stuff can make spectacular specimens (if kept in a jar of water) it is not for use. Any crack devalues opal -- like glass, if its not perfect its value is 10 - 15%. Even mines known for the stability of their stones keep the material for a year before offering it for sale. Many dealers keep their rough for a varying period before cutters get it. Most cut stones are held another six months to a year or more before being offered to the public. As the stone dehydrates with exposure, the surface can physically shrink on the still wet core causing a reticulated snakeskin fracture (crizzling, crisseling). Another, less understood mechanism involves stresses stored in the opal (much like un-annealed glass) which can release from the equilibrium being changed by cutting, result: a seemingly spontaneous crack. Perhaps this is the true source of opal's unfortunate reputation -- combined with a brittleness resembling glass, many stones didn't survive for the next generation. If your inheritance is a cracked opal, it is indeed bad luck! Know your vendor! |
| Generally opals should be cared for in the same way as pearls. (1) Don't bake them or leave them in the sun, (2) don't immerse them in dirty water, and (3) don't rub them with abrasives or dirty rags, or (4) smack them into hard surfaces. In addition, (5) bezel setting is generally preferred to prong (which can cause point pressure), (6) rapid temperature changes should be avoided, and (7) unsubstantiated reports indicate that bank deposit boxes have been implicated in cracking -- speculation includes extreme dry environment or sonic security devices as culprit. |
Composition of opal |
Glossary |
| Adularescence: a scintillating, often metallic, internal sheen Asterism: star stones, a floating star shaped adularescence Anhydratious: capable of dehydration Black opal: dark grey to black base color Catchalong: "stick to the tongue" water starved variety often changes color or transparency after brief immersion Color change: a shift in chroma apparent in different light sources, i.e., green to red in alexandrite in daylight vs. incandescent Color shift: pleochroism, different chromas when viewed through opposing axis Common opal: opal without play of color Contra-luz: "against the light" shows phenomenal color with transmitted light Coober Pedy: Australian minefield (opal was first found in Coober Pedy in 1915) http://www.opalcapitaloftheworld.com.au/ Crystal opal: usually refers to Australian white opal with a strong vitreous luster Doublet: two part sandwich; either opal with a dark backing material (glass, onyx, etc.) or more rarely with a clear top (quartz, synthetic spinel, glass, etc.) Field: source with multiple mines Fire: play of color Fire opal: oddly, opal without fire but with body color ranging from yellow to red, usually jelly opal Geyserite: common opal deposited by hot springs Girasol: translucent with a billowing blue fire Harlequin: angular mosaic fire Hyalite: transparent colorless common opal Hydrophane: See catchalong. Jalisco: Mexican state, generic source Jelly: highly translucent to transparent Lambina: Australian minefield Magdalena: Mexican city, opal field Matrix: host rock, usually silicatious Milk opal: highly translucent white Queretaro: Mexican city, opal field Myrickite: opal, chalcedony (var of quartz) with cinnabar inclusions [Trade name for a gray to white chalcedony or agate containing red inclusions of cinnabar from San Bernardino County, California. Although opal containing cinnabar has also been named myrickite, the preferred name is opalite >> ref Mitchell (1985,p.134) ] Play of color: fire, the shifting spectral chromas Pleochroism: different colors when viewed on opposing crystal axis Precious opal: opal with play of color Pseudomorphous opal: fossils replaced by opal -- wood, shell and bone. Rhyolite: matrix for the Oregon opal deposits, a tough material resembling jasper silicate Silica: SiO2, quartz, opal and obsidian Triplet: three part sandwich with opal center, a dark backing and clear top. See doublet. Water opal: transparent clear |
Copyright © 2006 Contraluzopal.com Bruce StJohn Maher, g.c.f.r.
Contraluzopal ~ Bruce Maher contra luz opal cutter, contra luz precious fire opal, cabochon color flash color play
| Bruce StJohn Maher, contra luz opal cutter and glass bead artist will present opals with fire, color play, color flash, and play-of-color. A result of Bruce's lapidary work and opal cutting. Contra luz opals presented. |