The Ruby Buying Guide – Quality Factors, Treatments & More!

How to Buy a Ruby

There can be lots of reason why you are looking to buy a Ruby, maybe for an engagement ring, birthday or anniversary present but it is always worth doing a bit of research and learning before setting out to buy one, which is why I wrote this short guide on how to buy a Ruby.

What is a Ruby?

It is always useful to understand a bit about a gemstone before you go and buy one, so here is a little bit of information about Rubies.

  • Rubies are part of the Corundum family and are the sister gemstone of Sapphire
  • Rubies measure 9 on the Mohs hardness scale. This means that Rubies are more resistant to being chipped or scratched than nearly all other gemstones except for Diamonds.
  • This combination of good durability and hardness means that Rubies are ideal for use in any type of jewellery and are a great alternative to diamonds for engagement rings.
  • Birthstone Month: July
  • Anniversary: 15th and 40th

Quality Factors the impact the Price of a Ruby


One of the the biggest factors that influences the price of a Ruby is the colour that the stone possesses. The most desirable colour is known as Pigeon Blood, which is a rich and vibrant red colour, although the description is a bit gruesome. This colour can be found in both treated and untreated Rubies but obviously is more desirable in untreated stones.

Outside of this, the colour in Rubies can range from pinkish reds to very dark maroon reds. On the pinkish end of the scale, there is no definitive line between what is a Pink Sapphire and what is a Ruby and it very much depends on the opinion of the person looking at the stone.


When you are buying a Ruby, ideally you want to buy a stone that is as free from inclusions as possible and there are a few reasons for this:

  • The Ruby looks more visually appealing and ‘cleaner’ to look at and with high quality stones, you may hear the term ‘eye clean’ used.
  • Stones with fewer inclusions are less likely to suffer from durability issues, although this is not always guaranteed.
  • The lower the number of inclusions, the more transparent the stone will appear. Heavily included stones can have a translucent to opaque appearance.

Now while inclusions are completely desirable, not all inclusions are bad as they can be used to help identify whether the stone is natural, treated or not and the origin of the stone. Some of the more desirable inclusions that can be found in Ruby are:

  • Silk – lots of small rutile needle inclusions that give an appearance similar to that of a piece of silk (mostly found in stones that haven’t been heat treated)
  • Fingerprints – the are partially healed fractures with a Ruby and can be found in both untreated and heat treated stones
  • Angular Colour Zoning – these are areas of colour concentration, from colourless/near colourless to a strong red colour within the stone and are produced when the crystal grows.
Silk Inclusion in Ruby (Img Credit: GIA)

Star Rubies

There is one occasion where inclusions are most definitely a good thing and that is Star Rubies.

This is an optical phenomenon found in some Rubies, where lots of Rutile needles grow parallel to faces of the natural crystal.

When these types of crystal are cut properly (always as Cabochons), the produce the optical effect known as a Asterism and this is where the light reflects off these needle inclusions to produce a 6 rayed star and on very rare occasions a 12 rayed star.

These Rubies usually have a very translucent to opaque appearance and the body colour usually isn’t the best.

Star Ruby (Img Credit: GIA)

Good quality star Rubies are very rare and thus highly desirable and valuable but this phenomenon can be replicated in lab created stones.


The most popular styles of cut for Rubies are Oval and Cushion cut as these provide the best yield from the rough crystals. With stones weighing less than 1ct, Rubies are available in many different cuts, with Round and Square stones are also popular in the smaller sizes.

To bring out the best colour in the stones, it is not unusual for Rubies to have deeper pavilions than you would find in a Diamond of the same size.


Ruby crystals generally don’t grow as big as Sapphires ones due to the way the crystals form, so finding really large examples of a Ruby is rare, especially if they have good colour and clarity. You will generally see price per carat increase quite a lot for good quality stones larger than 2 carats.


Most people will want an untreated stone as it adds more romance to the stone but in reality, it is estimated that over 90% of the Rubies for sale at any given time have been treated or enhanced in some way but there are good treatments and bad treatments. If the seller is claiming that the Ruby has not been treated, ask them for a lab report from a reputable gem lab that collaborates this.

Heat Treatment

Rubies have been heat treated for hundreds of years and all it involves is heating the stone up to a certain temperature in a controlled environment to either increase or decrease the colour of the stone.

The treatment is perfectly fine and is similar to what happens to the Rubies in nature, the results of heat treatment are stable and the colour won’t change over time.

Glass filling or fracture filling

Glass filled Rubies are something you really want to avoid as they are really low quality stones that have been filled with a high lead content glass to reduce the appearance of fractures.

Honestly best avoided as the glass can be removed from the stone if exposed to heat or chemicals and in some cases the removal of the glass can cause the stone to break into pieces.

Glass filled Rubies can be spotted by the blue flash that the stone shows when rotated and when looked at under magnification such as a jewellers loupe, the flash will be coming from within a fracture.

Synthetic & Glass Filled Rubies
Lab-Created Ruby and Glass Filled Ruby

Synthetic (Lab-Created) Rubies

A very important element in determining the value of a Ruby is whether the stone is natural or lab created. This is because lab created stones are worth considerably less than their natural counterparts.

And while the majority of buyers will want a natural stone, especially if they are buying fine jewellery, at the entry level of the scale, a lab created stone can be a good alternative to a low quality natural ruby.


The origin of a Ruby can have a big impact on the price of a Ruby. A Burmese Ruby will attract the highest premiums as it is the most desirable location. Very good quality stones are also come from Thailand.

In my opinion the recent discoveries in Mozambique have produced some of the finest Rubies ever found, some of them on a par with the finest Burmese Rubies.

Lab Reports

A lab report from a reputable lab such as GIA or SSEF will add value to a Ruby if it states it is a natural and whether or not the stone has been treated. A report is especially important when a location or lack of treatment is specified by the seller.

Ruby FAQ


So there it is, my guide to buying a Ruby. I hope that you have found this guide helpful as I have tried to include as much information that effects the value of a stone and also educate you to some of the different things that you may encounter when you are buying a Ruby.

And while you do want to buy the best stone that you can afford, you also want to buy the stone that you like, especially if you are buying it for yourself.

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