Ruby gemstones are valued for their rich, red color that denotes passion. This red hue takes on a variety of shades. Each ruby also has inclusions which makes each ruby unique. Even the name of the ruby was derived from the Latin word for red, “rubens.”
Gemstones colors are typically graded based on three factors. Hue, tone and saturation. Hue is the gradation of the color, for example dark or pale. Tone is the degree of absorption and reflection of light. For example tones can range from black to clear. Tone is the major determinant of the intensity of color. Finally, saturation is how much of the color of the stone comprises of the primary color. For rubies, those that are vividly and primarily red are most sought after.
Ruby colors can range from a deep blackish red to an orangish or pinkish red. Regardless of the combinations of other colors that can be a part of the ruby, the primary color is always red. Rubies that are on the shade of too dark can be the color of a wine color. The darkness of this ruby has a rich color but can have less sparkle. Rubies that pure red are often called “pigeon blood” or burmese red rubies. Their color is a lustrous, sparkling true red color. These rubies are the most prized and valuable of all rubies.
Burmese rubies posses a slight bluish tinge which is how they are distinguished. This term is an old one which probably originated in the gemstone industry in the 1800s. While not an exact or scientific term, "pigeon blood" is one that signifies topmost quality. While these types of rubies are most famously from Myanmar, the same quality can also be found in Tanzania, Mozambique and Vietnam.
Another common term used to describe slightly darker rubies is "royal red." These rubies are a shade darker than the "pigeon blood" rubies due to a higher iron content that occurs naturally within the gemstone. The higher iron content cuts the amount of blue transmission and fluorescence making the stone appear a shade darker. "Royal red" rubies can be found in Mozambique, Thailand, Cambodia, Kenya and Madagascar.
Rubies that are lighter have an almost pink hue. These are lighter and close to the color of a pink sapphire. Rubies can be pleochroic meaning that when tilted at various angles they can reflect different shades of color and have varying degrees of sparkle. Rubies also possess a fluorescence meaning that they will radiate when put under natural or artificial light. When looking at a ruby, your own eyes will be a great determinant of the quality of the red color. If your eye are seeing touches of gray or brown, the ruby may not be of the optimal quality.
Hue Tone & Saturation
Hue is where the color falls on the color wheel spectrum. The most basic and recognized colors by the eye are red, green, and blue. Other colors form when looking at intermediary colors between secondary colors like violet. Rubies that are closest to a true red on the color wheel spectrum are the ones that are the most prized in terms of their hue. The more secondary colors that are mixed into the ruby like purple, blue, or orange, the further the ruby moves away from having a perfect red hue. That being said, while some may consider a perfect red to be desirable, others may prefer the blending of colors or a ruby hue tinted with secondary colors. Saturation in the intensity of the ruby color. People tend be more attracted to highly saturated colors, meaning a vivid red for rubies. Saturation can also be defined as the richness of the color. Rubies benefit in that they have a natural fluorescence that makes them appear even more saturated with a glowing red color. A highly saturated ruby has a pure and intense red color. When looking at a ruby if it has low saturation, it is because there are undertones of gray, brown and black within the ruby. Gems of perfect saturation are rare and therefore more expensive. The tone is the amount of color in a ruby. Too much color and the ruby can appear dark, opaque and lifeless. Too little color and the ruby can appear, to be flat, glassy and not like the red color you expect. Medium tone is the most desirable for a ruby as it is the best balance of color and allows the sparkle of the ruby to come through. The right balance of tone and saturation is what really makes for a beautiful vivid blue sapphire.
While color is an important aspect, the transparency of a ruby is also an important factor in determining it’s value. Rubies that have many inclusions are difficult to see through. Common inclusions within rubies are called rutile needles. These needles are often referred to as silk as they are slender,and differently placed in each ruby. Rubies that have these inclusions are not transparent and therefore less valuable. The most valuable rubies have little to no inclusions and are easy to see through. Rubies that are more transparent also sparkle more vividly. Some of the largest factors affecting Ruby color are clarity inclusions and cutting. Rubies with many inclusions can either look too dark or very light, almost pinkish. Poorly cut rubies will not reflect color and light properly, making them look dull and dark or light and empty, like glass.
Rubies can also be treated to improve both their color and their clarity. The most common type of treatment is heat. This can improve the quality and consistency of the color. The appearance of inclusions can also be reduced with heat treatment. Other treatments also exist to fill the fractures and inclusions in a ruby. Rubies can be filled with molten lead glass which has a fairly similar look to real rubies. The majority of rubies are heat treated to improve their appearance. The heat treatment is permanent and is fairly common with all reputable ruby sellers. However, be wary of purchasing rubies that have treatments other than heat as they may not last over time. Rubies that are untreated and of high color and clarity carry a large premium and are several times more expensive than treated rubies. It is also difficult to find non-treated rubies of a high quality over 3 carats.