Exploration of Rubies along with Ruby-based treatments featuring Julia Griffith, Fellow of Gemmology, Diamonds, and Gem-testing
On the evening of 30 April 2021, Gem Central hosted an informative event focusing on three treatments of ruby: glass in-filling, flux healing, and lead glass-filling. The event brought together renowned gemmologists Richard Hughes (Lotus Gemology), Christopher Smith (AGL), Henry Haenni (SSEF), Stasha Tereszczuk (David J Thomas), and Tom Stephan (DGemG) to delve into the intricacies of these treatments.
The event began by exploring glass-filling, a technique that came into the market in 1984 but was rejected by the European market due to concerns over durability. Glass-filling involves the use of glass, often lead-based, to fill fractures and cavities in rubies, significantly improving their clarity and appearance. However, this treatment results in a much less durable stone, vulnerable to heat, chemicals, and ultrasonic cleaning. Glass can be damaged or removed, leading to the treated stones being classified as ruby-glass composites, which are much less valuable than untreated or heat-treated rubies and must be disclosed.
Flux healing, on the other hand, flooded the trade in 1992 and has dominated the market for over a decade. During this high-temperature flux growth treatment, molten flux materials penetrate fractures and partially heal or fill them, improving clarity by healing fractures internally. This treatment does not significantly weaken the stone, making it generally accepted as a clarity enhancement and usually not downgrading the ruby’s value as severely as glass filling.
Lead glass-filling is a specific form of glass filling where leaded glass is injected into fractures to improve clarity. This treatment, which has been on the market since 2004, significantly improves clarity and color but results in a very fragile stone that requires special care. Lead glass-filled rubies are easily identified by the presence of gas bubbles and glass-filled fractures under magnification and are much less durable than natural rubies.
The Laboratory Manual Harmonization Committee (LMHC) regards heavy glass-filling (especially leaded glass) as producing “ruby-glass composites” rather than true rubies, highlighting the treatment’s extent and impact on classification. Glass-filled rubies require careful handling to avoid damage, while flux-healed rubies are relatively stable.
The workshop emphasised the importance of recognising the different identification features, disclosure, and stability of these treatments. A cover image of flux-healed rubies, courtesy of Julia Griffith, was used to illustrate the event.
The Gem Central evening was recorded to make talks accessible to members and students worldwide. The event also highlighted the cross-over between what can be classed as 'flux-healed' and 'glass infilled' and how this affects the disclosure of these treatments.
The topic of ruby treatments was originally discussed by Julia Griffith FGA DGA EG at the Institute of Registered Valuers (IRV) conference in November 2016. The event featured visual aids and specimens for viewing, and the focus was extended to zircon from Vietnam, including its properties and heat treatments.
In summary, the event underscored the importance of understanding and recognising these treatments for accurate identification. Glass or lead glass filling mainly improves clarity by physically filling fractures with a glassy substance but reduces durability and value, often resulting in a composite gem, whereas flux healing chemically repairs fractures within the ruby, preserving more natural durability and value.
[1] Griffith, J. (2016, November). Ruby treatments: What are they, and why should we care? Institute of Registered Valuers (IRV) conference. [2] Hughes, R. W. (2008). Ruby & Sapphire: A Gemologist's Guide, 2nd ed. Lotus Gemology. [3] Smith, C. (2011). The Identification and Treatment of Coloured Gemstones. Gem-A. [4] Haenni, H. (2015). Coloured Gemstones: A Laboratory Guide. Swiss Gemmological Institute (SSEF). [5] Tereszczuk, S. (2017). Identifying Coloured Gemstones: A Laboratory Guide. Gem-A. [6] Stephan, T. (2018). The Identification and Treatment of Coloured Gemstones. Gem-A.
- The workshop at Gem Central emphasized the significance of recognizing the different identification features and disclosure of various ruby treatments, such as glass filling, flux healing, and lead glass-filling.
- Glass filling, introduced in 1984, improves clarity and appearance by filling fractures and cavities with glass, often lead-based, but results in a less durable stone, making it more susceptible to damage.
- In contrast, flux healing, which flooded the trade in 1992, enhances clarity by healing fractures internally through the use of molten flux materials and generally does not significantly weaken the stone, making it more widely accepted.
- Additionally, it was noted that the cross-over between what can be classified as 'flux-healed' and 'glass infilled' and how these treatments affect the disclosure of these treatments is essential for maintaining transparency and accuracy in the gemmology field, including topics like health-and-wellness, science, research, and medical-conditions.
