In the realm of precious gemstones, ruby stones stand out with their vibrant red hues, symbolizing passion, power, and prosperity. Highly revered in astrology, rubies have been associated with vitality and passion throughout history and across cultures. However, as the demand for this July birthstone outpaces natural supply, the market has seen an uptick in treated stones, including the increasingly common glass-filled rubies. Understanding the nuances of such treatments is crucial for wearers, aficionados, and casual buyers. In this blog, we uncover everything you need to know about glass-filled rubies. From specifics about the treatment process, to its impact on the value and durability of a ruby – here is a comprehensive guide to glass-filled ruby stones.
A Rough Ruby Crystal
What Is a Ruby?
Rubies or manik stones as they are known in India, are scientifically recognized as a variety of corundum, and are among the most coveted gemstones in the world. The presence of chromium within the crystal structure is responsible for this July birthstone’s distinctive red color, a feature that not only defines its identity but also contributes significantly to its allure. The intensity and tone of the red can vary from one ruby stone to another, influenced by the stone's geographic origin, the specific conditions under which it formed, and the concentration and distribution of chromium within its crystal structure. The value of a natural ruby stone is assessed based on a set of criteria commonly referred to as the 4Cs:
- Color: This is the most critical factor when evaluating a ruby's worth. The ideal color is a vibrant, almost fluorescent red, commonly known as Pigeon's Blood. This shade is characterized by a rich, deep red with just a hint of violet-blue undertones, which serves to intensify its appearance. The saturation and consistency of color throughout the stone significantly affect its value.
Rubies can occur in a colour span of light pink to a deep and vivid red
- Clarity: While rubies, like all gemstones, often contain natural imperfections called inclusions, the level and visibility of these features can impact the stone's clarity and, therefore, its value. Inclusions that do not severely affect the ruby's clarity or brilliance are less likely to detract from its worth. However, those that are prominent or negatively influence the stone's overall appearance can significantly reduce its value.
- Cut: The cut of a ruby stone refers to how the raw crystal has been shaped and polished into a finished gemstone. A well-executed cut will showcase the ruby's color, maximize its brilliance, and conceal its inclusions, thereby enhancing the overall appearance and value of the stone. The cut can range from traditional shapes like ovals and cushions to more intricate designs tailored to the unique characteristics of each ruby.
- Carat Weight: The size of a ruby stone is measured in carats, with one carat equivalent to 200 milligrams. Larger rubies are rarer and, therefore, significantly more valuable, especially if they also meet high standards of color and clarity.
Sources & Origins of Rubies
Natural rubies of high quality are exceedingly rare and, as a result, highly prized – both in astrology and for jewelry. This rarity stems from the specific geological conditions required to form rubies, which occur in only a few locations worldwide. The most renowned sources are Myanmar (formerly known as Burma), Mozambique, Madagascar, and Thailand, each known for producing rubies with distinct qualities:
- Burma (Myanmar): Burmese rubies are celebrated for their exceptional color, often described as "pigeon's blood." These stones are typically high in transparency and possess a glowing red fluorescence under sunlight, making them highly sought after and commanding premium prices. Burmese rubies are very limited in supply, and are widely considered to be the rarest types of rubies available in the market today.
- Mozambique: Mozambique has emerged as a significant source of high-quality rubies in recent years. The rubies from this region can rival the color and clarity of Burmese rubies but are often available in larger sizes. Mozambican rubies have thus become a popular alternative for those seeking sizeable, high-quality stones.
- Madagascar: Madagascar is home to some of the finest rubies and pink sapphires available in the market today. Although the quality of a Madagascar ruby varies, it is comparable to rubies from Mozambique, while being inferior to Burmese rubies.
- Thailand: Thai rubies tend to have darker hues with more brownish or burgundy undertones. While these stones may not command the same high prices as their Burmese counterparts, they are still valued for their unique beauty and are an essential part of the global ruby market. What is also essential to note is that most Thai rubies are lead glass-filled in order to enhance their physical appearance.
- Other Sources: Other sources of rubies include Vietnam, India, Tanzania, Kashmir, Afghanistan, and countries in Africa. Each of these regions produces rubies of varying qualities, and generally in smaller carat weights.
The combination of a ruby's natural characteristics, along with its geographic origin, plays a critical role in determining its overall value. The rarity of rubies that meet the highest standards across all 4Cs makes such stones some of the most expensive and desirable gemstones per carat in the world. As a result, natural rubies of exceptional quality are not only treasured as stunning pieces of jewelry but also as valuable investments.
What Are Glass-Filled Rubies?
Glass-filled rubies are a category of treated ruby gemstones that have undergone a specific enhancement process to improve their apparent quality and overall appearance. This method involves the incorporation of lead glass into the ruby's natural imperfections, such as fractures, cavities, and inclusions. Unlike traditional treatments that aim to preserve the stone's integrity, glass filling substantially modifies the ruby’s internal structure and composition. It not only fills the visible cracks but also bonds with the ruby, changing its physical properties.
The need for such treatment arises from the desire to enhance rubies that are otherwise considered too flawed for use in jewelry. These are typically lower-quality stones with significant natural defects that detract from their appearance and structural integrity. By filling these imperfections with a substance that closely matches the ruby's refractive index — a measure of how much the stone bends light — the treated rubies exhibit enhanced clarity and a more vibrant color. However, it's important to note that this process significantly alters the natural state of the ruby, affecting not only its aesthetics but also its value and durability.
Glass-Filled Rubies (left) have a more aesthetic appearance than untreated rubies (right), but are less durable.
The Process of Glass-Filling a Ruby
The creation of glass-filled rubies is a sophisticated process that requires careful handling and precision. Initially, the natural rubies are cleaned and prepared, typically involving a pre-treatment to remove any surface impurities. The stones are then placed in a crucible, a high-temperature container, along with a specific grade and type of lead glass powder.
This mixture is heated to a temperature where the glass melts but the ruby does not—usually between 900°C and 1,400°C (1,652°F to 2,552°F). At these temperatures, the molten glass becomes fluid enough to infiltrate the ruby's fissures and cavities deeply. The ruby and glass are kept at this heat for a period, ensuring thorough penetration and filling of the ruby's imperfections.
Once the heating process is complete, the mixture is allowed to cool, causing the glass to solidify within the ruby's structure. This cooling must be controlled to prevent the formation of new stresses within the stone that could lead to cracks or fractures. The result is a ruby with significantly improved visual characteristics, as the glass filler masks the original imperfections and enhances the stone’s overall clarity and color.
A Ruby before (left) & after (right) lead-glass filling (Source: First State Auctions)
Identifying Glass-Filled Rubies
Identifying glass-filled rubies requires a discerning eye and often, the use of specialized equipment. One of the hallmark signs of a glass-filled ruby is the presence of "flash effects" which are observable under magnification. These effects appear as bright, often blue but also multi-coloured flashes that contrast starkly with the ruby's natural coloration. They are caused by light reflecting off the surfaces where the glass filler and the natural ruby meet.
Blue Flash Effects in a glass-filled ruby
Another characteristic feature of glass-filled rubies is their altered surface condition. The filling process can sometimes leave a slightly bumpy or uneven surface, which can be felt with a probe or seen under high magnification. Moreover, the glass filler may react differently to heat, chemicals, and physical impacts compared to natural ruby material, leading to potential durability concerns.
A final check for a consumer to identify a glass-filled ruby would be its pricing. Glass-filled rubies are a lot more affordable than natural untreated rubies. This is because the diffusion of lead-glass within the ruby alters its chemical composition and hampers its durability, making the ruby inferior overall. As such, glass-filled ruby gems are a lot more affordable than their natural counterparts – often with a price difference of 100x or more between 2 specimens.
It is crucial for buyers and gem enthusiasts to understand these characteristics and identification methods. Recognizing glass-filled rubies allows for informed decisions, ensuring transparency and fairness in the gemstone market. While these treated rubies offer an affordable alternative to their natural counterparts, their care, handling, and overall value differ significantly due to the invasive nature of their enhancement. It is also important for any gem dealer to disclose any and all treatments that a gem may have undergone.
Impact of Glass-Filling on Ruby Value
The introduction of glass filling in the treatment of rubies has significantly impacted the valuation of these gemstones in several ways. Primarily, while making rubies more accessible to a broader market due to reduced costs, the glass-filling process also leads to a substantial decrease in their intrinsic value. This depreciation is rooted in the extent of the alterations made to the original gemstone, which can be considerable.
The value of a gemstone in the eyes of collectors and connoisseurs is largely determined by its naturalness, rarity, and the minimal extent of any enhancements. Natural rubies, especially those with minimal treatments, are highly prized for their inherent beauty and rarity, commanding high prices in the market. In contrast, glass-filled rubies are often sourced from lower-quality material that would not be marketable without significant enhancement. This vast difference in origin and treatment leads to a clear demarcation in value.
Buyers and investors should thus recalibrate their expectations when considering glass-filled ruby prices. While these stones offer the aesthetic appeal of more expensive, high-grade natural rubies, they do not hold the same investment value or prestige. As such, they’re beautiful to use for aesthetic and statement jewelry pieces, but cannot be considered investment-grade. It is critical for sellers to disclose the nature and extent of treatments transparently, enabling buyers to make informed decisions based on the actual worth and longevity of the stone rather than its superficial appearance alone.
Furthermore, the market for glass-filled rubies is nuanced. Factors such as the amount and visibility of the lead glass filler, the overall appearance of the stone, and the precision of the filling process can all influence price. Educated consumers who understand these nuances can better navigate the market, finding value in pieces that meet their specific criteria and budget.
Durability & Care
The durability of a ruby is significantly compromised by the glass-filling process, affecting both its physical robustness and chemical stability. Natural rubies, which rate highly on the Mohs Scale of Hardness (9 on 10), are highly durable and come second only to diamonds in hardness. However, the lead glass used to fill the ruby’s imperfections has different thermal and chemical properties compared to the natural ruby material, and as a result, glass-filled rubies are more susceptible to damage from heat, sudden temperature changes, and exposure to chemicals.
High heat can cause the glass filler to expand at a different rate than the ruby itself, leading to internal stresses and potential cracking. Similarly, harsh chemicals can react with the lead glass, causing it to deteriorate or become cloudy, thereby ruining the aesthetic of the gemstone. Even exposure to everyday substances like lemon juice or common household cleaners may damage the filler material.
Consequently, the care and maintenance of glass-filled rubies require extra caution. Owners should avoid using ultrasonic cleaners or steam cleaners, which are standard cleaning methods for many gemstones but can be disastrous for glass-filled rubies. Instead, they should clean these stones gently with warm soapy water and a soft brush, drying them thoroughly with a soft cloth.
Professional consultation is recommended for any significant cleaning or repair needs, as jewelers experienced with treated stones can offer the appropriate services without damaging the gem. Moreover, owners should be cautious with their jewelry, avoiding harsh impacts, high temperatures, and exposure to chemicals to maintain the stone's integrity and appearance.
Conclusive Reflections
In summary, while glass-filled rubies present an affordable alternative for those desiring the look of a more expensive gemstone, they require informed purchasing decisions and meticulous care. By understanding the impact of glass filling on both value and durability, consumers can ensure that they enjoy their ruby jewelry to the fullest, preserving its beauty for years to come.
If you’re looking to buy ruby online – whether for astrology or to wear ruby in jewelry, we invite you to explore Precious Earth’s curated collection of these gemstones. With a lifetime returns policy and a lab-certified guarantee of authenticity, you can rest assured of a genuine purchase at our web store. Our web store also includes a catalogue of a multitude of precious and semi-precious gemstones across 20 categories, including but not limited to sapphires, hessonite garnets, opals, emeralds, pearls, and more.
