Does a real opal's color change with viewing angle?
Yes, a real opal's color typically changes with viewing angle, an effect known as "play-of-color." This dynamic shifting of spectral hues is one of the defining characteristics of precious opals and a key indicator of authenticity.
The play-of-color in opals is caused by the microscopic structure within the gemstone. These structures are composed of tiny silica spheres arranged in a regular pattern. As light passes through the opal, it diffracts off these spheres. The angle at which you view the opal affects which wavelengths of light are diffracted towards your eye. This diffraction causes the flashes of different colors that appear to dance across the surface as you rotate the stone or change your viewing position. The intensity and variety of these colors contribute significantly to the opal's value. Synthetic or imitation opals often try to mimic this effect, but they usually fall short. In many imitation opals, the color is static, painted on, or created with materials that do not produce the same depth and dynamism as a natural opal. While some synthetic opals can display a color shift, it often has a "snakeskin" or "lizard skin" pattern which is a clear indicator of synthetic origin. Distinguishing natural opals from imitations often requires careful observation of the play-of-color under different lighting conditions and viewing angles, and sometimes magnification to see the internal structure.Are there specific patterns that indicate a fake opal?
Yes, certain patterns and visual cues are strong indicators of a fake or synthetic opal. These include a columnar or "snakeskin" pattern when viewed from the side, an unnatural uniformity or "too good to be true" brightness of color play, and the presence of distinct, unnatural patches or zones of color that lack the subtle blending seen in natural opals.
Fake opals, particularly those created using polymer-based methods, often exhibit a telltale columnar structure when examined closely from the side, especially in thicker pieces. This resembles stacked columns or a snakeskin pattern and is a direct result of the manufacturing process where microscopic silica spheres are arranged in a specific direction. Natural opals, on the other hand, form over millions of years with a much more random and complex arrangement, resulting in a more organic appearance. Another red flag is unnaturally vivid and consistent color play across the entire stone. While natural opals can be brilliant, they usually have variations and subtle shifts in color depending on the angle of light. A fake opal may display incredibly intense colors that seem almost fluorescent, with little or no variation as it's rotated. Furthermore, look for sharp boundaries between color zones. Natural opals typically blend colors gradually, whereas fakes may have abrupt transitions, resembling a painted effect. Finally, be wary of opals marketed as "opal doubles" or "opal triplets" without full disclosure. These are not entirely fake, but they consist of a thin slice of opal glued to a backing material (doublet) or sandwiched between a backing and a clear quartz cap (triplet). While these can be beautiful, they are significantly less valuable than solid opals and should be priced accordingly. Always inquire about whether an opal is solid, doublet, or triplet before making a purchase.How can I check for a glued-on doublet or triplet?
Examining the opal from the side is often the easiest method. Look closely at the point where the opal layer meets the backing (for doublets) or the backing and the clear top (for triplets). A distinct, straight line or a change in texture, color, or even a slight bubbling effect suggests the presence of glue. Also, look for a "step" or unevenness where the layers join.
Doublets and triplets are constructed to enhance an opal's appearance or allow for the use of thin, otherwise unusable opal slices. A doublet consists of a thin slice of opal glued to a dark backing, typically made of black onyx, potch (common opal), or sometimes synthetic material. The dark backing intensifies the opal's color play. Triplets go a step further by adding a clear quartz or glass cap over the opal layer. This cap serves to protect the thin opal and magnify the color, but it can also give the stone a glassy, unnatural appearance. Checking for glue lines requires careful observation under good lighting, ideally with a jeweler's loupe (10x magnification or higher). The glue line may appear as a thin, straight line, but it can sometimes be slightly wavy or irregular, especially in older or poorly made composites. If the top layer of a triplet is slightly lifted or damaged, you may be able to see the glue directly. Additionally, tap the stone gently against your teeth (if comfortable). A real opal will feel like a solid piece of glass, while a doublet or triplet might sound slightly duller or have a different resonance due to the layering of materials and glue. However, use this "tooth test" cautiously, as it can potentially damage the stone.What tests can I perform at home to identify a genuine opal?
While a definitive determination often requires a gemologist's expertise, you can perform a few simple tests at home to help differentiate between real and imitation opals. These include visual inspection under magnification, checking for consistent patterns or a "snake skin" effect (indicating a doublet or triplet), and assessing the opal's hardness.
First, closely examine the opal under magnification (a jeweler's loupe works well). Genuine opals display a vibrant play of color that shifts and changes as the viewing angle is altered. Imitation opals often have a static or "stuck-on" appearance to their color play. They may also exhibit a regular, repeating pattern, indicating a manufactured effect rather than a natural one. Look for signs of layering, especially at the edges. Doublets and triplets (common opal imitations) are constructed with layers of opal glued together with other materials (like glass or plastic). The "snake skin" effect along the edges is a giveaway sign. Finally, assess the hardness, though this test needs to be approached cautiously. Genuine opals are relatively soft (5.5 to 6.5 on the Mohs hardness scale). They can be scratched by materials like quartz or glass. Gently try to scratch the opal with a piece of glass. If it scratches easily, it might be a softer imitation, but be extremely careful as you could damage a genuine opal. If the opal scratches the glass, it could be a harder simulant like cubic zirconia or a synthetic spinel, materials sometimes used to mimic precious gemstones. Keep in mind that these tests are not foolproof, and a skilled imitator can produce convincing fakes. For valuable or uncertain opals, consulting a qualified gemologist for proper identification is always recommended.Is the price a reliable indicator of authenticity?
The price of an opal can be a *suggestive* indicator of authenticity, but it's not a foolproof guarantee. A very low price, significantly below market value for comparable opals, should raise a red flag. However, a high price doesn't automatically confirm an opal's genuineness, as unscrupulous sellers may inflate prices on synthetics or imitations to deceive buyers.
Price is just one piece of the puzzle. A genuine, high-quality opal with vibrant color play, a desirable pattern, and good body tone will command a significantly higher price than a common opal or a synthetic imitation. Factors like the opal's origin (e.g., Australian opals tend to be more expensive), size, and cut also heavily influence its value. A doublet or triplet opal, which are constructed from layers of opal and other materials, should be priced lower than a solid, natural opal of similar appearance. To accurately assess an opal's authenticity and worth, combine price considerations with thorough visual inspection, a seller's reputation, and ideally, a professional appraisal. Look for the characteristics of natural opals, such as irregular color patterns, natural inclusions, and a subtle depth within the stone. Question excessively uniform patterns or unnatural brightness, which are common traits of synthetic opals. Purchasing from reputable dealers with established return policies provides an added layer of security.How does the body tone relate to opal quality and value?
Body tone, referring to the opal's background color or base hue (ranging from black to white or colorless), significantly impacts an opal's value. Darker body tones, particularly black and dark grey, are generally more prized because they provide a stark contrast that accentuates the play-of-color, making the opal's vibrant hues appear more intense. This increased visibility and brilliance leads to higher value.
The relationship between body tone and value stems from the way light interacts with the opal's internal structure. A dark body tone absorbs more light, allowing the play-of-color to stand out prominently. In contrast, a lighter or white body tone reflects more light, potentially washing out or diluting the vibrancy of the colors. This difference in light interaction directly affects the visual appeal and desirability of the opal. Therefore, a gem-quality opal with a vivid play-of-color displayed against a dark background commands a premium price. It's important to note that while dark body tone typically increases value, this isn't a universal rule. Some opals with light body tones, such as crystal opals, can still be highly valuable if they exhibit exceptional clarity and intense, vibrant play-of-color. The overall appeal of an opal is a combination of factors, including body tone, play-of-color, pattern, brilliance, and cut. However, for otherwise comparable opals, the darker the body tone, the higher the likely value.What is "play-of-color" and how does it differ in real vs. fake opals?
Play-of-color is the mesmerizing display of iridescent colors that shift and change as an opal is viewed from different angles. In genuine opals, this phenomenon arises from the microscopic arrangement of silica spheres that diffract light, creating a dynamic and varied color display. In contrast, fake opals typically exhibit a play-of-color that is static, uniform, or artificially produced, often lacking the depth and complexity found in natural stones.