Yes, some fake opals do exhibit a color change effect, while others do not. The specific properties depend entirely on the material used to create the imitation. It's crucial to distinguish between different types of "fake opals" to understand their visual characteristics.
Understanding "Color Change" in Opals
Before diving into imitations, it's important to clarify what "color change" means in the context of opals. Natural opals are renowned for their play-of-color, a unique optical phenomenon where spectral colors flash and shift across the stone as it is moved or as the light source changes. This is due to the diffraction of light by microscopic silica spheres within the opal's structure.
In contrast, some "fake opals" might exhibit a general shift in hue or a translucent glow under different lighting conditions, which is a simpler "color change effect" rather than the dynamic play-of-color seen in genuine opal.
Types of Fake Opals and Their Color Properties
The term "fake opal" can refer to a wide range of materials, from lab-created versions that closely mimic natural opal to simple glass imitations. Their ability to display a color change effect varies significantly.
Oparex (Plastic Material)
Oparex is a plastic material that exhibits some color change effect. It's sometimes mistakenly referred to as synthetic opal, but it's important to understand that Oparex is a plastic and not a lab-grown version of actual opal. Its color shift is typically less complex and vibrant than the play-of-color found in natural or high-quality synthetic opals.
Glass Opalite
Glass Opalite is a commonly known imitation opal. This material is essentially a type of glass that does not show any play of color. Instead, Glass Opalite often possesses a milky, translucent appearance that can appear to glow with a bluish hue against dark backgrounds or an orangey glow when backlit. It simulates common opal, which lacks play-of-color, rather than precious opal. More information on opalite can be found on resources like Mindat.org.
Synthetic Opals (Lab-Created)
High-quality synthetic opals, sometimes called lab-created opals, are manufactured to closely replicate the chemical and physical properties of natural opal. These materials do exhibit a vivid play-of-color that can be very convincing. They are typically made from silica and water, similar to natural opal, but under controlled laboratory conditions, resulting in a more uniform structure. While they mimic the play-of-color, their patterns are often too regular or columnar compared to the unique and varied patterns of natural opals. You can learn more about synthetic opals from institutions like the Gemological Institute of America (GIA).
Other Imitation Opals
Various other materials have been used as opal imitations over time, including:
- Foil-backed glass or plastic: These generally show no intrinsic color change, relying on the foil for a reflective shimmer.
- Slocum Stone: An early plastic imitation that could show some iridescence but not true play-of-color.
- Glass with iridescent coatings: These might show a surface rainbow effect but lack the depth and internal play of natural opal.
Distinguishing Fake Opals from Natural Opals
Telling the difference between natural opals, synthetic opals, and other imitations can be challenging but is possible with careful observation.
| Feature | Natural Opal | Synthetic Opal | Oparex (Plastic) | Glass Opalite (Glass) |
|---|---|---|---|---|
| Play-of-Color | Brilliant, irregular, unique patterns | Strong, often columnar or very uniform patterns | Some color change effect (less dynamic) | None (milky glow, no flashing colors) |
| Structure | Irregular, varied silica spheres | Very ordered, often columnar silica spheres | Uniform plastic matrix | Solid glass, sometimes with swirls or bubbles |
| Hardness (Mohs) | 5.5-6.5 | 5.5-6.5 | Varies, generally lower (e.g., 2-3) | 5-6 |
| Weight/Density | Relatively light | Similar to natural | Lighter than natural | Heavier than natural |
| Temperature | Cool to the touch | Cool to the touch | Warmer, like plastic | Cool to the touch |
| Common Flaws | Cracks (crazing), inclusions | Rarely any natural flaws, often too perfect | Can show mold marks, bubbles | Swirls, gas bubbles |
| Internal Pattern | Organic, diverse | Can appear "snake-skin" or highly regular | Simple, uniform | Sometimes hazy, consistent |
Practical Tips for Identification:
- Examine the pattern: Natural opals have unique, often irregular play-of-color patterns. Synthetic opals often display a highly ordered, columnar, or "snake-skin" pattern.
- Check for uniformity: If the color flashes are too uniform or arranged in perfect columns, it's likely synthetic.
- Look for inclusions/imperfections: Natural opals may have minor inclusions, while synthetics and plastic imitations tend to be flawless. Glass opalite might have tiny bubbles.
- Touch test: Plastics like Oparex will feel warmer to the touch than natural or synthetic opals, which feel cool.
- Magnification: Under magnification, the structure of silica spheres in natural and synthetic opals can be observed, while plastic or glass imitations will show a different texture or internal characteristics.
Why is "Color Change" Important?
The presence and quality of "color change" (or play-of-color) are paramount in determining an opal's authenticity, beauty, and value. Genuine play-of-color is a marvel of nature, making natural opals highly sought after. Understanding these distinctions helps consumers make informed purchasing decisions and appreciate the unique characteristics of each material.
