Rubies were treasured by early cultures as they represented the redness of the blood that flowed through their veins, and many believed that rubies held the power of life and so were often carried into battle for protection. To the spiritually inclined, such as is the case for people of Hindu faith who composed the earliest written accounts of ruby or “ratnaraj” (meaning “king of the gemstones” in ancient Sanskrit), the gem is as radiant as the “sun new risen” and “paints the whole house with crimson”.
Rubies vary in colour more than you might expect, from brownish-red to orangey-red to purplish-red to pinkish-red. Neither too dark nor too light, and evenly distributed throughout the gemstone.
Traditionally, the most prized colour of rubies are a vivid crimson with a hint of blue. As with all gemstones the colour should be even throughout. The appraisal and appreciation of colour is, of course, subjective to some extent. Rubies from different origins often have distinctive colours although each deposit can have a range in hues. Mozambican rubies are quite unique in their formation as the region produces rubies that are in many ways similar to those found in each of the other key producing nations, thereby spanning breadth of the know colour ranges.
A gemstone’s clarity has to do with the number of inclusions that it contains, the size of those inclusions and their position within the gemstone. The fewer, smaller and less conspicuous the inclusions, the better. Importantly, however, inclusions should not always be seen as being “bad” as they are also responsible for giving each gemstone its unique character. It is rare to find exceptional clarity even in high-quality rubies. Look instead for a gemstone with good transparency – that is, an ability to transmit light.
In a good-quality ruby, however, there should be no “ugly” inclusions – none that are distractingly obvious when looking directly through the top of the gemstone. Nor should there be so many that they affect the gemstone’s ability to reflect light. If there are, the gemstone will seem dull and flat. A ruby that is relatively free of inclusions will have lots of brilliance, life and sparkle. This is particularly important if the gemstone is faceted – though less so if it is a cabochon, in which case the colour is far more important than the clarity.
Occasionally the presence of inclusions in a ruby can have a spectacular and highly desirable effect: that of asterism. Asterism (from the Latin for star) is caused by inclusions of the mineral rutile. If arranged in the right formation, these inclusions will reflect light in a beautiful star-like pattern, which is revealed when the gemstone is cut as a cabochon or a bead. These so-called star rubies may have four- or six-armed stars; those with six are the most sought-after. It is usually easy to detect a synthetic star ruby, as the arms of the star will be suspiciously neat in comparison with a natural example.
Ruby is classed as a 9 on the Mohs scale – making it second in hardness only to diamond – and also very tough, so the options for cutting are practically unlimited. Cushions, ovals and rounds are the most popular cuts, as they tend to make the most of the colour and size of the gemstone; hearts, marquises and baguettes less so.
If a ruby is well cut, it will mask colour variation, inclusions and other imperfections, and not create “extinctions” (dark patches). Badly cut gemstones tend to maximise weight at the expense of brilliance.
The gemstone should be well proportioned and symmetrical, with no distortions. It should have sharp facet edges and flat faces – reflections should enter the eye at once, not “roll” across the face – and be free of chips and scratches.
When polished well the gemstone should also possess very good lustre – in the case of rubies, the desired quality is known as “bright vitreous”.
The value of a ruby can sometimes be greatly increased by treating it to improve its appearance. Some such treatments are fully accepted within the industry, while they should always be disclosed, and others less so – these treatments generally include dyeing, filling, heating, irradiation and diffusion.
Check for concentrations of dye in any cracks in the gemstone – dye is used to improve inconsistent or weak colour.
Filling is sometimes visible too, depending on the size of the filling at the surface of the gemstone – it is possible to see a difference in lustre or, if the gemstone had been filled with high-lead-content glass, a flash of blue may be noticed when inspecting the gemstone in strong light.
Diffusion treatments may be detected (as long as it’s not beryllium diffusion) by immersing the gemstone in water – the colour will fade towards the centre when immersed.
The presence of joining lines along the edges could reveal a “composite” ruby. If in doubt, put the gemstone in water – you will see a distinct line at the join.
The use of heating and irradiation is harder to spot, but is increasingly common. When a ruby is heated – typically almost to melting-point – its crystal structure is effectively reformed, permanently altering the colour of the gemstone.
The extent to which a ruby has been treated will affect its value – one with good natural colour and clarity will always be more valuable than one whose qualities have been artificially enhanced.
FC Gems rubies are sold with full disclosure of any treatments to which they may have been subjected. Wherever you buy your rubies, ask the seller for details.