Ruby Gemstones – How to Assess Quality

Natural ruby - untreated

How do you assess the quality of a ruby gemstone?

From the earliest times, precious gemstones such as rubies, emeralds and pearls have adorned many of the richest and most regal of people. Kings, Queens and Emperors, were the privileged few who could afford gemstones for jewelry and ceremonial decorations like crowns and coronets: rubies were for royalty.

However, these days, whilst a ruby is still one of the most expensive gemstones, you don’t need to be wildly rich or regal to afford one. Nevertheless you do need to be able to assess their quality.

Ruby gemstones are now a popular choice for many people who want an alternative to a single diamond – or like an element of color. Ruby red is evocative not only of fire and passion but also of the warmth of deep love – and is therefore an ideal gemstone for an engagement ring.

The Color of Rubies:

The best ruby rings have a very specific red color – a rich purplish, carmine red that has a warm, fiery glow. The brightest and most valuable red rubies are called pigeon blood-red rubies and command a large premium over other rubies of similar quality.

However, colors of rubies can vary considerably and are viewed by a jeweler in terms of their “hue”, “saturation” and “tone”

The hue: The hue of a ruby can vary from light orange to red and through to a deep purple.

The saturation – also known as intensity or purity: some rubies can be masked by brown or gray, which is undesirable.

The tone: is the degree of color from light to dark in the ruby.

Natural rubies:

The ruby is one of the hardest natural gemstones and belongs to a class of minerals called Corundum – which is a form of Aluminium Oxide. Rubies are one of the hardest natural gemstones, second only to diamonds in hardness.

largeovalrubyThe deep red of ruby is due to the presence of a small amount of chromium that gives it the rich red coloration. However, if the corundum has other impurities such a iron or titanium, it will give the ruby a blue color. When the corundum becomes blue, it is called a Sapphire.

Whilst diamonds have a color grading system, rubies do not. Selecting a ruby by color is therefore generally very much down to the eye of the jeweler.

Clarity and Inclusions:

The other aspect to take into account, when buying a ruby is it’s clarity.

Rubies are prone to a range of different inclusions – or blemishes.

Some of the common blemishes found in rubies are:

  • Silk: these are fine fibers of other minerals, such as titanium oxide, that resemble silk strands. When these are found they indicate that the ruby is of natural origin and has not been subjected to heat treatment
  • Needles – also known as rutile needles: long thin crystals or gas and liquid filed tubes
  • Cracks: fractures and fissures. Healed fractures often look like fingerprints
  • Color zoning: these are growth layers that developed as the corundum crystal formed and create distinct areas of color that show as concentric hexagonal zones and uneven patches of color

Almost all rubies available for sale nowadays as jewelry are described as “natural”. However it has become common practice to treat the stones in some way – usually using some form of heat treatment. This enhances the color and the clarity of the stones.

Many of the lower priced rubies on the market have been treated artificially with heat, fracture filing and flux healing to repair fractures and inclusions and also to improve the gemstone’s color. This is now regarded as common practice in the business and seen as perfectly acceptable.

However, there are some jewelers who still supply stones in their natural condition and eschew such artificial methods of enhancing the quality of the original stone. These truly natural stones command a higher price than similar treated stones of a similar size and quality.

Some jewelers adopt a grading for their stones. Below is the grading scheme used by Angara, one of the companies that supplies truly natural stones.

A – Good

AA – Better

AAA – Best

AAAA – Heirloom

Gemstones are scrutinized far less severely for clarity than diamonds.  

With rubies, emeralds and sapphires – and all other gemstones – the main criterion is usually whether the gemstone is eye clean or not. In other words, by just viewing the gemstone with your naked eyes, can you locate any inclusions (blemishes) in it?

Gemstones by their very nature, generally have far more inclusions than diamonds and thus it is not required to use a 10x magnification as a means of measurement as is used for diamonds. 

The value of a ruby, a sapphire or an emerald is determined by how visible any inclusion is  to the naked eye. Even so, there is very little difference in the price between stones which are eye clean and stones which have no inclusions visible even under a 10x magnification. With diamonds, color, clarity, carat weight and cut play an equal part in determining its value. However, with rubies (and for sapphires and emeralds also) color plays a significantly bigger role than clarity in determining the value of the gemstone.

A Suggested Checklist for Assessing the Quality of a Ruby Gemstone.

Given that Rubies are one of the rarest and most desired gemstones in the world, investing in a ruby should therefore be approached with care.

1) The Color

Color is probably the most important feature – well at least the first consideration – when assessing the value of a ruby piece of jewelry. You need to look at its actual color (the hue) the intensity of the color (the saturation) and its tone – the amount of color the ruby contains, which can range from very light to very dark.

People prefer different colors and no one color is superior to another. Even so, the closer the color is to a vivid blood red, the more valuable it is seen to be.

2)  Clarity

It is very rare to find a ruby that is perfectly clear: most natural rubies have some imperfections and even cloudiness. Better quality rubies are transparent not opaque.

Nowadays, it is thought that nearly all rubies are heat treated to enhance clarity. This has become accepted practice within the industry.

3)  Identify any blemishes 

Distinguish between an inclusion and a blemish. The latter is an imperfection on the surface of the ruby; inclusions are flaws within the gem and it is unusual to discover a ruby that does not have inclusions. Deposits of rutile, a mineral composed mainly of titanium dioxide, is the most common inclusion found in rubies. 

Beware of any ruby that is free of inclusions; it will certainly have been heat treated  and could even be synthetic. Inclusions are the fingerprints that distinguish between natural and synthetic gemstones.

4)  Sparkle

Observe the stone’s sparkle. This will help determine the quality of its cut: the better the sparkle, the better the cut is the usual rule of thumb.

Avoid poor quality cuts such as the fish eye, which creates a ruby that is almost see-through instead of one that reflects a sparkle of light back towards you. Seeing a dark patch or faded appearance in the middle of the stone means its cut is too shallow or too deep. The most common cuts seen in rubies are round, oval and cushion although many others are available.











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