Ruby is a red variety of the mineral corundum and is one of the most expensive gemstones. It is also one of the most durable gems, with a hardness rating of 9 on the Mohs scale (diamond is a 10). The highest quality rubies come from Burma, Madagascar, Sri Lanka, Thailand, Kenya and Vietnam.
Evaluating Ruby Color
Color is one of the most important factors determining ruby quality.
When choosing among stones, be sure to evaluate each of these color characteristics:
Hue: The primary hue of ruby should be red. This stone often exhibits other hues such as orange or violet.
It is worth noting that a secondary hue of purple can underscore the red color of ruby, but what hue you would prefer comes down to personal taste.
Tone: This characteristic refers to how dark the color of the gemstone is.
The most valuable rubies tend to have medium darkness, i.e. they are not so dark as to appear almost black. Look for rubies that are not too light or too dark.
Saturation: Color saturation refers to how intense the hue of the stone is. With ruby, stones that have an intense red hue are more valuable than those whose color is not as vivid.
It is expected that a ruby will have some inclusions inside it. Make sure they are as few as possible, though.
Although you cannot expect a ruby to be perfectly flawless, the highest quality gemstones will be eye-clean, i.e. there won’t be any flaws visible with the naked eye.
There is a ruby variety called “star ruby” that gets its beauty from its inclusions. These stones are polished as cabochons (i.e., they are smooth, without facets) and reflect light in the form a six-ray star – an optical effect caused by a web of tiny inclusions (also called “silk”).
Evaluating the Cut of Ruby
Gemstone cut is an important consideration for several reasons.
First, the cut’s proportions determine how pleasing the stone will look to the eye.
Also, the way a stone is cut affects how it reflects light so as to create brilliance and sparkle.
And there is also the durability factor: Poor cut proportions can make some parts of a gem more likely to chip or break under pressure.
Rubies are available in all sorts of cuts, but the most sought-after stones are the round ones, which are also more expensive. Round cut rubies should not be too deep or too shallow when looked at from the side.
The general rule of thumb is that the depth of a round stone (also referred to as its height) should be 60% to 80% of its width (as measured by the diameter of the stone’s widest part – the girdle).
Stones of lower clarity are often cut as cabochons. These rubies should be evaluated similarly to the ones cut with facets: Look for symmetry and some transparency coupled with a nice luster.
You should keep in mind that it is nearly impossible to devise a framework of precise rules to judge cut as there are different opinions as to what a perfectly cut stone should look like. In general, when evaluating cut, you should be looking for stones that are proportional and have good sparkle.
Treatments and Enhancements of Rubies
Many rubies sold today have been treated to enhance their color or clarity. Most commonly, rubies are treated with heat to improve their red color; the results of this type of treatment are usually permanent. Sometimes, rubies are also dyed.
Another common treatment is filling rubies with material that masks their inclusions and makes the stones look more transparent.
Rubies can also be coated with substances that make their surface flaws less visible, but you should know that this film will wear off at some point.
Regardless of what treatments a stone has undergone, its enhancements should be disclosed, so you should always ask whether a ruby has been treated before you buy it. It is best if the stone comes with a certificate that verifies whether it has been enhanced.
In general, rubies with high clarity and top-quality color are more expensive if they are natural; treated varieties should be cheaper than them.
Ruby Imitations and Synthetic Rubies
There are some gemstones that look like ruby and can be used as its imitations. For example, red garnet is one of the stones that can pass for ruby. Red colored glass is also used as an imitation.
Unlike imitations, synthetic rubies have the same chemical structure as natural rubies. Synthetic rubies are created in a laboratory, but they are still real rubies, although artificial ones.
Created rubies have higher clarity than natural ones and are more affordable.
General Ruby Shopping Tips
When buying ruby, it is best if the stone comes with a certificate that proves its authenticity and origin. This is especially true if you are paying a lot of money to buy a natural high-quality stone.
Make sure that you ask about all treatments the ruby has undergone and how these enhancements affect the way you should wear it and care for it. Also, don’t forget to ask whether the ruby you are buying is natural or artificially created.