Everything you need to know about Opal Gemstone
Opals are unparalleled in their beauty and value. Opal is a peculiar species that even has its specialised terminology. There is no other gem quite like an opal because each opal is unique. Among the most popular gemstones, opals are also the most fragile. Therefore, they require special maintenance and care.
The Romans considered opal the most valuable and potent stone due to its ability to reflect a variety of hues. According to Bedouin mythology, opals were thrown from the sky during electrical storms because they were infused with lightning. When opals were first mined commercially in Australia in the 1890s, the country swiftly became the world's leading supplier of this October birthstone.
Description
Play-of-colour, a phenomenon exclusive to opal, makes this gemstone so popular. Opals fall into two general categories: precious and common. In contrast to common opal, precious opal exhibits play-of-colour.
Like Australia's "outback," seasonal showers in semiarid areas result in opal formation. The rains poured into the old rock below the earth, bringing dissolved silica (a combination of silicon and oxygen).
A lot of the water evaporated during dry times, leaving behind silica deposits in the crevices and between the sedimentary rock layers far below the surface. In a nutshell, silica deposits are responsible for Opal formation.
Opal's play of colour results from its tiny spheres arranged in a grid, much like Ping-Pong balls in a box. Light waves diffract, or bend, as they pass between the spheres. As they curve, they disperse into a spectrum of hues. The end product is a vibrant display of colours.
The hue you observe shifts as the spheres become larger or smaller. Small spheres, on the order of 0.1 microns (one ten-millionth of a metre) in diameter, are responsible for the violet colour. Spheres of 0.2 microns in size generate red light. Sizes create the remaining hues of the rainbow in between.
Gem opals are classified in numerous ways by professionals, but the five most common are as follows:
- Bodycolour: White or light opal; transparent to semitransparent; has colour play against a white or light grey background.
- Opal with varying degrees of transparency and colour play set on a black or other dark background is known as a black opal.
- Fire opal is a type that can range from transparent to translucent and has a brown, yellow, orange, or red body tone. This stone is also known as "Mexican opal," although it rarely displays play-of-colour.
- Boulder opal can range from transparent to opaque, and its colours can play off a light or dark background. Matrix refers to the bits of the surrounding rock that make up the gem.
- Translucent to partially transparent, like crystal or water opal, with a see-through appearance. The kind in question exhibits vivid and unusual colour shifting.
Facts
| Absorption Spectrum | Birefringence | Birthstone |
| Most none. The green line is at 660 nm; the cutoff is at 470 nm. | None | October |
| Colour | Crystallography | Etymology |
| Colourless, white, yellow, orange, and red (various shades), yellowish brown, greenish, blue, grey, black, and violet. | Amorphous. New research indicates that opal comprises a network of microscopic spheres or a solidified gel; it frequently forms concretions; it is botryoidal, reniform, and stalactitic. | From the Latin name, opalus, for this stone is possibly derived from the Ancient Greek opallios for "colour changing." |
| Cleavage | Dispersion | Enhancement |
| None | Very low | Impregnation, dyeing, surface coating. |
| Formula | Fracture | Fracture Luster |
| SiO2 · nH2O. Water= 1-21% in opal, usually 6-10% in precious opal. | Conchoidal to uneven | Waxy, Subvitreous |
| Luminescence | Occurrence | Optics |
| Green fluorescence in opal is often due to included U minerals. Much opal fluoresces strong white in SW, LW, sometimes with persistent phosphorescence. (See table below.) | In sedimentary rocks or where low-temperature solutions bearing silica can percolate through rocks. | Isotropic; N: 1.44-1.47. Mexican opal as low as 1.37, usually 1.42-1.43. |
| Heat Sensitivity | Luminescence Present | Luminescence Type |
| Very | Yes | Fluorescent, Phosphorescent, UV-Long, UV-Short |
| Lustre | Mineral | Mohs Hardness |
| Vitreous, pearly, waxy. | Hydrated Silica | 5.5-6.5 |
| Phenomena | Specific Gravity | Typical Treatments |
| Play of colour. In rare cases, it can display chatoyancy or asterism. | 1.99-2.25. (Orange-red variety, ~2.00; black and white opal, 2.10; green opal, 2.12). | Dyeing, Infusion/Impregnation, Surface Coating |
| Pleochroism | Refractive Index | Transparency |
| None | 1.37-1.47 | Transparent to opaque |
| Varieties | Variety of | Wearability |
| Common Opal, Fire Opal, Precious Opal | Best Known Gemstones | Poor |
History
Opals have been compared to volcanoes, galaxies, and explosions by authors. Unique opals were given lyrical titles like "Pandora," "Light of the World," and "Empress" by their many admirers. A symbol of affection and future promise in ancient Rome. Romans used the word 'opalus,' which meant "precious stone," to describe this gem.
Pliny, a Roman scholar who lived from 23 to 79 AD, made the following observation on opals in 75 AD: "Some opali carry such a drama inside them that they rival the darkest and richest hues of painters." Some "recreate the dazzling blaze of burning oil," while others "recreate the scorching inferno of burning sulphur." He was astonished that this multicoloured gemstone included all the rainbow hues.
Opal has been attributed to magical properties and origins by many cultures. According to Arabic mythology, it is struck by lightning as it descends from above. The ancient Greeks believed that opals had healing properties and might even grant the bearer the ability to foretell the future. The Europeans have always seen the gem as a representation of optimism, innocence, and the truth.
The opal is the traditional birthstone for October. Legend has it that only October babies should wear opals. Contrary to popular perception, this urban legend originates in a novel written in the nineteenth century rather than in folklore or personal experience (Anne of Geierstein by Sir Walter Scott). Opal's capacity to show every colour has made it the most enchanting and lucky stone of centuries. Moreover, some initially thought it might keep blonde hair looking healthy and shiny for longer.
Stone Size
Large and exceptional opal stones and rough have been given individual names, just as rare and valuable diamonds. Here are a few examples of famous works:
- Uncut, the Coober Pedy Olympic Australis weighed 127 oz.
- Andamooka Noolinga Nera weighs 86 ounces in raw and 205 carats in an oval shape.
- Two thousand six hundred and ten carats of Roebling Opal were found in Nevada's Rainbow Ridge (in the Smithsonian Institution).
- Lightning Ridge, Australia; 252 fragments; the world's most famous light source.
- Butterfly or Red Admiral Cut; 40-50 carats rough; Lightning Ridge, Australia. This opal is considered by many to be the most stunning of its kind.
- The Lightning Ridge, in Australia, 226, has been hacked up.
- Australia's Lightning Ridge is the location of Pandora's 711th shard.
- White opals (345), 155, and 83 carats; 58.8 carats of black opals (Nevada), 54.3 carats of colourless opals (Mexico), and 44 carats of black opals (Australia) are all on display at the Smithsonian Institution in Washington, DC (pale yellow-orange, precious, Brazil).
Stone Care
Although Opals are fragile but are well worth the extra attention they require, due to their sensitivity to temperature shifts and "crazing" inclination, they sometimes crack or "craze" when they dry out. (Checking is the technical term for surface cracks.)
Water-soaked opals can't be cut into facet shapes until they dry out. Over time, opal rings can lose their vibrant colour and become ghostly white. Scratches on the opal's surface can dull the colour play and ruin the polish, but good polishing should fix the problem.
It's essential to keep in mind that opals are more susceptible to cracking and chipping than other popular gemstones. Since they have a hardness of only 5.5, they are prone to scratches. Therefore, an opal shouldn't be worn as a ring stone unless it is in a protective setting, is part of a triplet, or is only worn on rare occasions.
FAQs
1. How much is an opal worth?
The value of an opal stone depends on many different characteristics. Reasons for such a wide variety in price include variations in the gem's nature, provenance, colour, patterns, fire, rarity, and transparency. However, the average cost per carat can be anywhere from $1 AU to $193 AU.
2. What is the rarest colour of opal?
Due to their shallow frequency and great value, opals with a "black" (or "dark") body tone are the most valuable and uncommon. You can find Rainbow colours in black opals. They have a black complexion that brings up the vividness of the opal's face colours.
3. What does opal symbolise?
Opal has a long history of being valued as a lucky and benevolent talisman. In the Middle Ages, people thought wearing an amulet containing opal would guard against deteriorating vision and boost your mind and memory.
4. Can opal only be found in Australia?
Although opal can be found in other places such as Brazil, Mexico, Honduras, and the western United States, Australia is responsible for creating 95% of the world's precious opal and claims it as its national gemstone.