Ruby is a beautiful gemstone that can be found in a variety of color ranges.
The most prized rubies are those that are a deep red color.
However, some rubies may have other colors, such as pink, orange, or purple in them.
In order to bring out the best color in a ruby, many gemologists heat treat their rubies at the detriment to its value.
This is a gamble that they are willing to take because a ruby of poor quality will not sell otherwise.
Treating a gemstone is now considered a trade standard for colored stones.
This practice flooded the market in the 1960’s and has became a standard when it was realized that poor quality rubies could still sell in a market where untreated stones were so rare.
Ninety-five percent of all colored gemstones in the modern marketplace have been heat treated.
There are worse things to do to a ruby however, such as glass filling. However, even heat treatment has its perils too.
Here are three things you need to know about heat treating rubies!
Table of Contents
What Is Heat Treatment and How Does It Work?
Treating a ruby is done to improve both clarity and color of rubies.
This is a stable and permanent treatment in which the effects will not fade due to wear or cleaning.
A ruby that comes from Sri Lanka becomes more intense red, and a ruby that comes from Thailand will lose its brownish color.
Other rubies that have a dark unattractive core will lose that dark core in favor of a more distributed red color.
One of the main intentions of heating a ruby is to change the silk structure by dissolving it at a high temperature until it recrystallizes and dissolves inclusions. This results in deepening the color as well as “removing” inclusions that would normally make a ruby opaque rather than translucent.
To heat treat rubies, they are placed in a crucible and heated to extreme temperatures of between 1600 to 1800 degrees.
The heat will dissolve any rutile inclusions inside the stones which will improve the clarity as well as the color.
The Benefits of Heat Treating Rubies
While there are some benefits of heat treating rubies, they must also be contrasted with the risks which include a significant drop in value unless the rubies were deemed as being unusable for making jewelry altogether.
First, let’s look at the potential benefits:
Heat Treating Makes Rubies Affordable
Heat treating rubies will possibly make them more marketable in the cases of those which would otherwise not be used in jewelry.
This will help to salvage and level out the investment cost for mining and cutting.
There is a market for rubies that are merely red in color regardless of treatment, and those will be found in pieces that are usually mounted in less expensive metals.
Heat Treating Makes Rubies Look Better
Improves the saturation of color as well as removing unwanted hues.
If a ruby has a poor disbursement of color, it would not be used in more expensive jewelry, but if heated, it can result in a much nicer color and would sell for a higher price.
Likewise, if a ruby has brownish hues, heating will remove those hues while at the same time making the reds more vivid.
FYI, heat can be applied two ways, either hotter to darken color, or low heat to lighten the color of a gemstone that is too dark.
Heat Treating Can Remove Inclusions
Dissolves silks and fills in cracks or fissures.
Heating a ruby can get rid of a lot of the silk inclusions that block translucency while at the same time, it can also serve to fill in the fine fissures and hairline cracks that would make a ruby less stable.
The Risks of Heat Treating Rubies
Not everything is great when it comes to heat treating rubies.
There are some definite risks that should be considered before heat treating a ruby, such as destroying them or significantly reducing their value. Here’s how:
Heat Treatment Can Damage Rubies
Too high of heat can cause stress fractures and halos around the natural inclusions within the gemstone, which then become an identifying characteristic. This is because expansion occurs at different rates within the stone.
Heat Treatment Can Make Rubies Lose Value
Heating rubies have allowed more rubies to flood the market, thereby reducing the natural rarity of rubies.
Whereas rubies were discarded when they had poor quality, they are now kept for marketing after heat treating.
This results in rubies having a wide fluctuation in market pricing that must take into account the alterations.
Because a heated ruby has had artificial improvements in appearance, the market for vastly more expensive unheated rubies has diminished.
Why pay for an expensive unheated ruby when the less expensive, but heat treated, ruby is just as beautiful?
Heat Treatment Can Make Rubies Brittle
Heating rubies makes them more prone to chipping and less durable.
Because it is difficult to know how high the temperature was used to heat the ruby, then it is very possible that the amount of heat used could have been high enough to damage them internally.
Unless you know what you are looking for in terms of damage, you may be buying a ruby that is beautiful in color but is as fragile as an emerald.
Should Rubies Be Heat Treated?
Heating rubies is a regular practice of the mining industry.
It is used to push more rubies out to markets that would otherwise not be able to sell for a profitable amount compared to the cost of mining.
There is a tension between marketing rubies so that the average person can own a beautiful red gemstone, and those who have more means that would rather hold out for a natural unheated gemstone which is far more expensive.
However, one thing that has happened in the marketplace is that heating is so common that it is no longer seen as a factor for lowering a price!
Pricing for heated rubies have slowly crept up to those of unheated rubies over the decades because they have been able to shed their original stigma, and because there are so few unheated rubies left that are for sale.
How To Tell If A Ruby Has Been Heat Treated
Unless you have an experienced trained eye or are in the gemology business, you may actually have to rely on a jewelry store who should know exactly what they have in their inventory.
If you go to a jewelry store and tell them that it is important to know if a ruby has been heat treated or not, they should direct you to a Certified Graduate Gemologist who will know for certain due to all the following tell-tale signs:
Disk-like Inclusions
Look for disk-like fractures with lace-like outer healing rims. This is caused by expansion of natural crystal inclusions.
Burned Inclusions
Look for burned or altered mineral inclusions. These will appear with rounded and often whitish snowball or cotton appearances because of the expansion of the gasses in these areas.
“Broken Silk” Inclusions
Look for broken silk, or partially “reabsorbed” rutile needles. These look like dark lines that have been bent or kinked.
Two-Phase Crystals
Look for ruptured two-phase inclusions and negative crystals.
Two phase crystals appear like one crystal coming out of another and is caused by the expansion of different minerals at different rates. Negative crystals are voids that have been created from this process.
Sintered Surfaces
Look for sintered surface areas especially around the girdle. Sintering is the fusing of small particles together and appears as a smooth glassy surface.
FAQ’s About Heat Treated Rubies
What is a natural enhanced ruby?
The word “natural” is a loaded word because lab grown rubies are natural also, in that they start from the seed of a ruby, are rapidly grown in a laboratory setting rather than in the earth, and are the exact same chemical and composition as earth mined rubies are.
A natural enhanced ruby is a ruby that was earth mined (as opposed to lab grown) and has had either heat or filling enhancements to make it more attractive.
This enhancement should be noted on documents so that you know exactly which enhancements that a particular ruby has undergone because this will have a dramatic effect on the value and cost.
What percentage of rubies are heat treated?
Rubies in the market today are 95% heat treated.
It is a rare thing to find ones that are not, but it is very possible if you know where to look.
Usually, jewelry made before the 1960’s can have rubies that are not heated such as in vintage and antique jewelry.
This is how we find untreated rubies, because a ruby dealer generally will have a difficult time finding them too.
Are glass filled rubies worthless?
Glass filled rubies are really no longer rubies.
When it comes to the world of gemstones, there are many different ways to enhance them to make them more attractive such as with heat and chemicals, but when you start adding other materials to the stone, it is no longer considered that same thing.
You should be paying for the mounting rather than the ruby.
Are unheated rubies worth more?
Unheated rubies are a fantastic find!
They are far more rare than diamonds and are highly sought after by people who have the means to buy them.
If someone says that the ruby you are considering buying is unheated, then they should be able to offer you written proof from a Certified Gemologist. Otherwise, it is best to take your business elsewhere.
Final Thoughts
Whether or not you think heat treated rubies are valuable is entirely up to you.
Some people believe that the process of heating a ruby actually improves its quality and makes it more beautiful, while others believe that it is a way to cheaply enhance a gemstone.
In the end, it really comes down to personal preference.
If you want our opinion, we think that unheated rubies are very rare and valuable. If you value rarity and want to own a piece of history, then we recommend buying an unheated ruby.