Rubies are among the most revered and valuable gemstones, distinguished primarily by their vibrant red color. While this deep red is their most recognized feature, the exact shade and intensity can vary considerably. These variations contribute to each ruby’s unique character.
The Iconic Red
The most sought-after color for a ruby is “pigeon’s blood” red. This pure, vivid red has a subtle purplish undertone, intense saturation, and often a glowing appearance. It is considered the benchmark for ruby quality and commands the highest prices. The “pigeon’s blood” designation originated in Burma (now Myanmar), a primary source of these exceptionally colored stones.
This deep, intense red is prized because it represents the ideal balance of hue, tone, and saturation. Rubies with this color exhibit a captivating richness that is neither too dark nor too light. Its inherent brilliance and interaction with light contribute to its legendary status.
Color Variations and Nuances
Beyond the ideal “pigeon’s blood,” rubies exhibit a range of red hues that are genuine. These variations can include orangey-red, purplish-red, and even pinkish-red tones. While pure red is generally the most prized, the presence of these secondary colors can result in beautiful and valuable gemstones.
The value of these variations depends on the intensity and prominence of the red. For example, orangey modifiers are generally less desired than purple ones. Pinkish-red rubies are also common, though the distinction between a light pinkish-red ruby and a pink sapphire can sometimes be debated. Regardless of the specific undertone, the dominant color of a ruby must always be red.
The Science Behind the Hue
The red color of rubies originates from the presence of chromium within their mineral structure. Rubies are a variety of the mineral corundum. Trace amounts of chromium ions replace some of the aluminum atoms in the corundum crystal lattice during the gem’s formation.
This chromium absorbs certain wavelengths of light, allowing red light to be transmitted and reflected. The concentration of chromium directly influences the intensity of the red color; higher chromium content generally leads to a stronger red. Other trace elements, such as iron, can also influence the specific shade and saturation.
Identifying Genuine Rubies
Distinguishing genuine rubies from other red gemstones or imitations is important. Several other red stones, such as garnets, spinels, and tourmalines, can be mistaken for rubies due to their similar appearance. Pink sapphires, a variety of corundum lacking sufficient chromium to be classified as rubies, are another common point of confusion.
Gemologists use various methods to differentiate rubies. Rubies are exceptionally hard, ranking 9 on the Mohs scale, second only to diamonds. This hardness helps distinguish them from softer imitations. Professional gemological tools can measure properties like refractive index and specific gravity, which are unique to rubies. Additionally, natural rubies often contain small internal characteristics or inclusions, which can be observed under magnification, confirming their authenticity.