Rubies are graded using the same four criteria as are used to grade diamonds. All four criteria for evaluating diamonds are adequately defined and equally weighted. However, rubies are colourful gemstones with no globally recognised quality standards. Furthermore, because the colour is the essential attribute in rubies, the requirements are different.
Follow along as we look at the best qualities for certified ruby based on each of the four requirements to know:
Colour diversity in rubies has historically proven difficult to describe. Gem merchants have had to rely on descriptive terminology that isn't commonly recognised or understood for ages. Rubies were categorised in ancient Indian writings as "China rose," "saffron," "pomegranate," and "partridge eyes." The best Burmese rubies were supposed to have the colour of "pigeon's blood," while rubies from Mozambique and Madagascar can also attain this level of quality. Today, geologists are looking for a more general and objective way to evaluate the colour of rubies. The hue, tone, and saturation of their colour and the colour of other coloured gemstones are now used to describe them.
All three of these terms are included in the definition of the perfect certified ruby colour–vivid, medium-dark red to slightly purplish red. The hue is the gem's primary colour. While the primary hue of a certified ruby is red, secondary colours such as purple or orange can also be observed. Although pure red is the optimum colour, many fine Myanmar rubies are somewhat purplish red. The quality of a ruby is regarded to decline when the tint turns progressively purple or orange, and the ruby loses value.
In the gemmological industry, the colour boundaries of rubies are hotly debated. Actual gemstones are the most excellent way to analyse and compare the colour of a certified ruby. To determine if corundum is genuine "ruby" or pink, purple, or orange sapphire, many gem labs utilise a collection of master stones. Tone and saturation must be considered while distinguishing between rubies and pink sapphires. The value of a certified ruby is also influenced by tone, which specifies how light or dark a stone's hue is.
The tone of most fine rubies is medium to medium dark. However, the colour of certified ruby should not be so dark that it is obscured, nor should it be so light that it appears diluted or indistinct. Because of their dark tone, particular Thai rubies have a "garnet red" tint. On the other hand, even if the colour saturation is intense, the stone may be mistaken for a pink sapphire if the tone is too light.
Saturation is vital in establishing a ruby's value since it describes how pure or potent a colour appears.
Color inducing trace element chromium is found in greater abundance in rubies with high saturation levels. They can achieve very saturated hues without becoming dark. Brownish red is the colour of ruby with low saturation. Rubies with "vivid" saturation are the most valuable, although rubies with "strong" saturation are equally valuable. A certified ruby's colour can be affected by a variety of other things. If a ruby can glow, its red colour can be enhanced.
Inclusions can also improve a ruby's colour. For example, rutile silk needles are highly reflective and scatter light within the stone, potentially improving the colour. The colour of a ruby can also be affected by how it is cut. Skilled gemstone cutters cut rubies to optimise brilliance, eliminate colour zoning, and display their best pleochroic colour.
Star rubies are available in various pink and red hues, but the most popular colour is the same vibrant, medium-dark red found in transparent faceted stones.
On the other hand, Star rubies rarely achieve the bold, deep red of the greatest transparent stones due to their high silk content. Those few that do will command a hefty premium.
Rubies don't always have the same great clarity as beautiful diamonds. Even the best rubies, when studied under 10x magnification, are likely to contain inclusions. A ruby with no imperfections, on the other hand, should be regarded with caution; it could be a synthetic stone or a glass replica. The best clarity grade for ruby is "eye-clean," which indicates there are no apparent inclusions. When assessing the clarity, experts analyse the size, number, placement, and general visibility of the inclusions. Crystal growth produces inclusions as a natural by-product.
Certified Ruby inclusions differ depending on their source or origin, as well as their treatment history. Reflections from the rutile needles form a six-rayed star when a ruby with abundant silk is cut as a cabochon.
Star rubies can have up to twelve rays because of hematite needles, which creates a doubling effect. Star rubies never acquire the degree of purity possible in faceted stones because the star's appearance is dependent on silk inclusions. However, the more translucent a star ruby is, the more valuable it is. The state of a ruby's silk can reveal a lot about the stone's treatment history.
Many rubies are heated to change their colour or improve clarity. Silk is partially melted or decomposed by the intense heat used to prepared rubies. Intact silk shows that ruby has not been heat-treated, whereas deteriorated silk, visible under magnification and recognisable by a qualified gemologist, indicates that ruby has been heated.
Weight in Carats
While a five-carat aquamarine may be considered modest, fine five-carat ruby is large enough to attract serious gem collectors' attention. Certified Ruby prices per carat rise with carat weight, just like any other stone. Although fine quality rubies above one carat are uncommon, commercial quality rubies are widely available in various sizes.
Because fine quality certified ruby raw is exceedingly expensive, premium stones are rarely cut to calibrated sizes to avoid substantial weight loss. Rubies of commercial quality are more likely to comply with calibrated sizes.
A carat (abbreviated "ct") is a unit of weight used to represent the size of a certified ruby. A carat is a metric unit that equals one-fifth of a gramme (.20). A point (abbreviated "pt") is a hundredth of a carat. A total carat weight (abbreviated "etc.") is calculated by weighing several tiny rubies together. A one-carat certified ruby will appear smaller than a one-carat diamond due to its high specific gravity. They want the gem's perceived colour to be as bright as possible.
Pleochroic indicates that the colour of rubies changes according to the angle from which they are seen. Rubies are typically cut so that the ideal hue is evident through the crown of the stone, as consumers prefer a purplish red colour to orange-red colour. By enhancing a stone's brightness, or the amount of light returned to the viewer's eye, a talented gem cutter can also impact the stone's apparent hue. They want the ultimate weight of the diamond to be as high as possible. The crystal habit or growth form of the ruby may limit this. They want to hide any unwanted additions or colour zoning as much as possible. They're needed to meet the demand for specific designs or cutting styles among consumers. These guiding concepts may at times be at odds with one another. Cutters may be required to sacrifice colour or clarity to maintain carat weight on rare occasions. For example, it may not orient a ruby for optimal colour since the weight loss would be prohibitive.
In other cases, an asymmetrical cut may be permitted because it maximises colour, conserves rich ruby rough, and avoids strongly included or shattered areas inside the crystal.