rubies
RUBIES
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Introduction
Rubies: Composition, Formation, and Origin
Where Are Rubies Found?
Color is Most Import
Clarity
Factors Influencing Rubies Value
Ruby Durability
Rubie Value: Natural, Treated, and Synthetic Comparisons
Ruby Treatments
Treatment Grading and Disclosure
Key Questions to Consider Before Buying a Ruby
Rubies are one of the three precious colored gemstones, alongside Emeralds and Sapphires. They are a variety of the mineral corundum, distinguished by their vibrant red color, which is caused primarily by traces of chromium. While corundum can appear in other colors — such as blue (sapphire) or pink (also sapphire) — only the red variety is called ruby. Rubies are treasured for their intense color, exceptional hardness, and historical significance. Known for their captivating beauty, rubies hold a special place among gemstones, celebrated for their deep, fiery hues and enduring symbolism.
Rubies: Composition, Formation, and Origins
Rubies: Composition, Formation, and Origins
Rubies belong to the corundum family, which also includes all sapphires. While sapphires can come in many colors, rubies are defined specifically by their rich red hue. The presence of chromium gives rubies their unmistakable color, ranging from pinkish red to deep blood red.
Chemical Composition and Crystal Structure
Rubies are composed of aluminum oxide (Al₂O₃), with chromium as the trace element responsible for their red coloration. The exact shade of red depends on the chromium concentration and the presence of other elements like iron. Rubies have a trigonal (hexagonal) crystal system and typically form as prismatic or tabular crystals. Their structure, combined with their exceptional hardness (second only to diamonds at 9 on the Mohs scale), makes rubies one of the most durable gemstones available.
Despite their hardness, rubies may contain natural inclusions formed during their intense geological growth process. These inclusions, sometimes called “silk” when composed of fine rutile needles, are often viewed as signatures of a ruby’s natural origin.
Formation of Rubies
Rubies form under conditions of intense heat and pressure within the Earth’s crust, typically in metamorphic rocks like marble or in basalt-associated deposits. In marble-hosted rubies, low iron content allows for the formation of the highly saturated, pure red colors prized by connoisseurs. Basalt-hosted rubies, often containing more iron, can display darker tones.
The ruby’s vibrant color, rarity, and strength all result from these challenging formation environments, which require specific combinations of pressure, temperature, and chemistry.
Where Are Rubies Found?
Rubies are sourced from several renowned regions, each known for producing stones with distinct qualities:
Myanmar (Burma): Burmese rubies are considered the finest in the world, renowned for their vivid “pigeon’s blood” red color, a pure, rich red with a hint of blue. The legendary Mogok region has produced some of the most valuable rubies ever discovered.
Mozambique: Mozambique has become a leading source of rubies in recent years. These stones often display vibrant red to slightly purplish-red colors and can offer exceptional clarity.
Thailand: Thai rubies are known for their darker red tones, sometimes described as “garnet-like,” often with higher iron content that can dull the brilliance slightly.
Other sources include Vietnam, Sri Lanka, and Tanzania, each offering rubies with unique variations in color and clarity.
COLOR IS MOST IMPORTANT
A ruby is appreciated and graded above all by its color. It is the ruby’s vibrant red hue that most significantly determines its value.
A richly saturated ruby will consistently command higher prices than a larger ruby with less desirable color, despite the rarity of large stones.
Ruby color covers a narrower range compared to some gemstones, primarily spanning from pinkish-red to deep, blood-red. The most sought-after rubies display a strong, vivid red with minimal secondary hues. If a stone is too pink or too purple, it may be classified as pink sapphire rather than ruby, affecting its value.
The finest rubies exhibit intense color saturation without being too dark or too light. Their glow can seem almost electric, with chromium creating the luminous red tones for which rubies are celebrated.
| Origin | Typical Color | Notes |
|---|---|---|
| Myanmar (Burma) | Vivid red to “pigeon’s blood” red | Extremely prized for its rich color with minimal secondary hues; warm, glowing red that remains luminous even in dim light. |
| Mozambique | Vibrant red to purplish-red | Slightly purpler undertones may appear; high clarity and brilliance are typical; strong alternative to Burmese rubies. |
| Thailand | Deep, darker red | Sometimes garnet-like; higher iron content can reduce fluorescence and slightly mute the color. |
| Vietnam | Bright red, sometimes slightly pinkish | Can resemble Burmese rubies; vibrant stones with good transparency. |
| Sri Lanka | Pinkish-red to medium red | Often lighter in tone; more affordable; can show excellent transparency. |
Clarity
Rubies, like emeralds, are Type II gemstones, meaning that some inclusions are expected and accepted. Eye-clean rubies are rare and extremely valuable.
Typical inclusions include rutile silk, needles, crystals, and fingerprint patterns. Fine rubies with minimal visible inclusions can command premium prices.
Unlike diamonds, ruby clarity is judged by the eye, not a loupe. Minor inclusions are acceptable as long as they do not significantly impact the stone’s transparency or brilliance.
Factors Influencing Ruby Value
Hue: The ideal ruby hue is pure, vibrant red. Stones that are too pink or too purplish may lose value.
Saturation: Fine rubies possess strong, vivid saturation without appearing overly dark or brownish.
Tone: Ideally, rubies have a medium to medium-dark tone. Stones too light may be classified as pink sapphires, while too-dark stones can appear less lively.
Color Consistency: Uniform color across the stone, without zoning or patches, greatly enhances a ruby’s value.
| Inclusion Type | Description | Common Source |
|---|---|---|
| Rutile Silk | Fine, needle-like inclusions that can create a soft glow (asterism in star rubies) | Myanmar, Vietnam |
| Crystals and Mineral Inclusions | Small internal crystals or mineral inclusions | Myanmar, Mozambique |
| Color Zoning | Uneven distribution of color | Thailand, Mozambique |
| Fingerprint Inclusions | Fluid or crystal-filled patterns resembling fingerprints | All ruby sources |
| Twinning Planes | Internal growth lines that can create optical effects | Myanmar, Vietnam |
Ruby Durability
Rubies rank 9 on the Mohs scale, making them incredibly durable and suitable for daily wear. Their excellent toughness means they resist scratching and chipping better than most colored stones, second only to diamonds.
While inclusions can sometimes create weak points, a well-cut and properly set ruby can remain stunning and resilient for generations.
Rubie Value: Natural, Treated, and Synthetic Comparisons
Untreated Rubies:
Rubies in their natural, untreated state are exceptionally rare and highly prized. These stones have not been altered to improve their color or clarity.
Untreated rubies with vivid red color and good transparency can command the highest prices in the gemstone market.
Treated Rubies:
Most rubies undergo treatments to enhance their color and clarity. Heat treatment is the most common and accepted method, improving both appearance and durability without significantly diminishing value when properly disclosed. Some lower-quality rubies may be subjected to more intensive treatments, such as glass-filling, which do impact their market value.
Synthetic Rubies:
Synthetic rubies are lab-created stones with the same chemical and physical properties as natural rubies. While they can exhibit excellent color and clarity, they lack the rarity and natural formation history of genuine rubies and are thus priced much lower.
Ruby Simulants:
Simulants are imitation stones that look like rubies but are composed of different materials, such as red spinel, garnet, or glass. While they may resemble rubies visually, they do not share their durability, brilliance, or value.
Ruby Treatments
Heat Treatment:
The vast majority of rubies are heat-treated at high temperatures to improve their color and clarity. This process enhances the ruby’s vibrancy and reduces the visibility of inclusions.
Purpose: To intensify the red hue and improve transparency.
Stability: Heat treatment is permanent and generally accepted in the gemstone industry.
Disclosure: Reputable dealers always disclose heat treatment.
Lead Glass-Filling:
Some rubies of lower quality undergo filling with lead glass to improve clarity by filling fractures. While this makes heavily included stones look more appealing, it drastically lowers the value compared to untreated or lightly heated rubies.
Purpose: To make heavily fractured rubies appear transparent.
Stability: These stones are fragile and should be treated carefully (avoid heat, chemicals, ultrasonic cleaning).
Important Note:
Untreated rubies, or those subjected only to traditional heat treatments, are far more valuable than rubies that have been glass-filled or otherwise heavily treated. Always request a reputable laboratory certificate when purchasing high-value rubies.
When purchasing emeralds, it’s important to know the extent of any treatment, as it directly affects the gem’s market value and longevity. Reputable laboratories grade treatments as follows:
None: The emerald has not undergone any treatments, making it highly valuable and rare.
Minor: Only a small amount of oil or resin is used to fill fractures. These emeralds are considered high-quality and retain most of their value.
Moderate: A moderate amount of treatment is applied, often visible under magnification. While still beautiful, the emerald’s value is lower than that of untreated or minimally treated stones.
Significant: Extensive treatment has been performed, typically involving larger fractures and more visible treatments. These emeralds are usually more affordable but are considered less desirable by collectors.
Key Questions to Consider Before Buying a Ruby
When evaluating a ruby, consider these key questions to guide your purchase:
Color: The most critical factor. Ask for a description of the ruby’s hue, saturation, and tone. Inquire about any secondary hues (such as purple, orange, or pink) that may influence its value.
Clarity: Rubies often contain inclusions. Ask if the inclusions are eye-visible and whether they affect the stone’s brilliance or durability.
Cut: Ensure the ruby is well-proportioned to maximize color, brilliance, and overall beauty while minimizing the visibility of inclusions.
Treatment: Ask if the ruby has been heat-treated (a common and accepted practice) or if other treatments (like fracture-filling or diffusion) have been applied, which can affect both value and durability.
Origin: Rubies from Myanmar (Burma) are traditionally the most prized, but excellent rubies also come from Mozambique, Vietnam, Thailand, and Sri Lanka. Ask about the stone’s geographic origin if available.
Certification: Always request a certificate from a recognized gemological laboratory (such as GIA, AGL, or GRS) to confirm authenticity, disclose any treatments, and, if determined, specify the origin.