Hello, gemstone enthusiasts! Welcome to another video summary post on gemstone treatments. Today we’re diving deep into the world of blue sapphires, specifically examining whether they’ve undergone lattice or chemical diffusion treatments or if they’re simply heat-treated.
Why Are Sapphires Treated?
Before we delve into the testing process, it’s important to understand why sapphires are treated in the first place. Almost 95% of sapphires on the market today are heat-treated to enhance their color and overall appearance. The level of treatment can vary from mild (known as normal heat treatment) to more extreme methods such as titanium or beryllium diffusion, also referred to as lattice diffusion.
The intensity of the treatment significantly impacts the price. For instance, a sapphire with normal heat treatment might cost around $1,500 per carat, while a beryllium-treated sapphire could be as low as $15 per carat. The primary reason for these treatments is to make the sapphire more visually appealing and thus easier to sell.
Heat Treatment vs. Chemical Diffusion
Heat treatment can make a sapphire appear more vibrant, adjusting its natural color to be more marketable. However, chemical diffusion, which involves introducing elements like beryllium or titanium into the stone, can go a step further. This method can either intensify the sapphire’s existing color or completely alter it.
Distinguishing between normal heat treatment and chemical diffusion is crucial for buyers and sellers alike. While there are visual tests that can offer clues, these are not foolproof. The most accurate way to determine if a sapphire has undergone chemical diffusion is through advanced lab testing using methods like SIMS (Secondary Ion Mass Spectrometry) or LA-ICP-MS (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry).
Testing the Sapphires: A Step-by-Step Guide
To illustrate this process, I recently examined two blue sapphires purchased for a custom pair of earrings. The goal was to determine if these sapphires had been treated with normal heat or if they were chemically diffused. Here’s how I conducted the test:
Immersion in Water: I immersed the sapphires in a bowl of water and used the microscope’s overhead light to get a diffused white light setting. Ideally, methylene iodide (R.I.=1.76), which has a refractive index closer to that of sapphires (R.I.=1.76), would have been used instead of water (R.I.=1.33). However, water, with its lower refractive index, can still provide useful observations, even though it is less clear.
Observing Color Gradients: According to a GIA study, the key to detecting lattice diffusion lies in observing color concentrations and gradients within the sapphire. Natural color zoning in sapphires does not conform to the faceted shape of the stone, whereas chemically diffused sapphires often show surface-conformal color layers.
Comparing Treated and Untreated Stones: I compared two large, round sapphires with normal heat treatment against two smaller, oval sapphires that had been beryllium diffused. The difference was noticeable—while the naturally treated sapphires displayed more angular, non-conformal color zones, the diffused sapphires showed more centralized color concentrations with less angular zoning.
Microscopic Examination: Under the microscope, I examined the sapphires for additional clues:
Conclusion: The Importance of Lab Testing
While these visual and microscopic tests can offer valuable insights, they are not 100% accurate. The only way to be absolutely certain whether a sapphire has undergone chemical diffusion is to send it to a specialized lab for advanced spectrometry testing.
I hope this post has provided you with a clearer understanding of sapphire treatments and the importance of proper testing. If you’re considering purchasing a sapphire, always ensure you know exactly what you’re getting. And remember, when in doubt, consult with a reputable gemologist or gem lab.
Thank you for reading, and feel free to share your thoughts in the comments below. Stay tuned for more gemstone insights, and have a great day!
Reference:
Link: https://www.gia.edu/gems-gemology/summer-2003-beryllium-diffusion-ruby-sapphire-emmett
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