Heat Treatment
- Nature of gemstone: Almost any gem material can be heated, except those that are affected by heat such as emerald and opal.
- Materials used: Equipment can be a cooker, furnace, kiln, muffle, pot, oven, roaster, brazier etc. The heating agents used include gases, oils, charcoal, wood, coal, heating coils etc.
What is heat treatment for gemstones?
Heat treatment is most commonly used to alter color but is also used to increase clarity. Rubies and sapphire can require significantly higher temperature to alter color and change clarity. Heating is used to either lighten, darken or alter the color of a gem. Amethyst is heated to lighten its color.
What is an example of heat treatment in jewelry?
An example of this is the dissolving of rutile silk inclusions in blue sapphires, which improves both clarity and color. This heat treatment is permanent and irreversible.
What do you need to know about gem treatment?
The following guide will give a short description of the treatment process, some gems for which the process is used, how easy or difficult the treatment is to detect for a trained gemologist, how often the treated gem might be encountered in the jewelry trade, and how durable the material is to normal handling procedures.
What happens if you don’t heat treat gems?
Heat treatment is the most common treatment and without heat treatment the availability of fine gems would be significantly less. With less gems prices would be dramatically higher only available to the rich. This is the reason untreated gems often command 30% to 50% higher prices.
What happens when you heat a gem?
Heating is used to either lighten, darken or alter the color of a gem. Amethyst is heated to lighten its color. Heat a little more and some sources of amethyst will alter color from deep purple to orange colored citrine. Uraguay is a good example.
Are heated gemstones less valuable?
Heat-treated gemstones are not necessarily valued less, but unheated gemstones do carry a premium, especially if good quality. Quality is a slightly separate subject however, as regardless of whether a Ruby or Sapphire is heated or not, the quality grading system remains the same.
How do they heat treated amethyst?
To create heat treated Citine (also called burnt Amethyst), an Amethyst crystal is baked at temperatures of around 800-900 degrees Farenheit, this changes the colour to deepening shades of orange, depending on how long it is "cooked" for.
Do heat treated gemstones fade?
The color of a heat-treated sapphire will remain permanent and will not change or fade unless the stone undergoes a secondary treatment. This is the reason why heat treatment on sapphires is accepted by most retailers.
How do you tell if a ruby has been heat treated?
However some natural rubies if very poor quality in the first place can have 'flux enhancement' and these stones are literally held together by glassy filler. However they are quite easy to tell and if you are looking at a ruby that has been heat treated you will not seen any filler or noticeable enhancement.
What happens when Amethyst is heated?
When the temperature is lower than 360 °C, the amethyst color does not change significantly. As the temperature rises to 380 °C, the violet color begins to fade out and gradually becomes colorless. Then it changes to light green at 420–440 °C.
Why did my amethyst turn white?
If you leave your amethyst in sunlight or under other UV sources for too long, its color will fade. And if you expose amethyst to heat, you'll see the color fade as well.
Why is my amethyst turning green?
The green color is usually caused by heating of amethyst (natural or artifical). The white quartz (milky) color is caused by numerous fluid or gas inclusions in clear quartz - they could also overwhelm an amethyst color.
Is Black Rose quartz heat treated?
Stones such as Moonstone and Rose Quartz are typically not treated. However, some natural stones—like Amethyst, Topaz, Citrine, Sapphire, Ruby, Aquamarine, and Tanzanite—are usually heated after they're recovered from the earth.
Are heat treated sapphires less valuable?
Heating is an accepted treatment for sapphire. But for fine-quality sapphire, confirmation from an independent laboratory like GIA that there is no evidence of heat adds to a sapphire's rarity and value.
What is the difference between heated and unheated gems?
You will get a more vibrant, saturated stone for your budget if you choose a heated sapphire. Most heated sapphires are eye-clean, with no inclusions visible to the naked eye. Unheated sapphires will have whatever inclusions were naturally created within them.
How can you tell if a sapphire has been heat treated?
5:176:49How to check the difference between Unheated vs Heated Sapphire ...YouTubeStart of suggested clipEnd of suggested clipAs the color on the sapphire with natural heat only has improved in clarity as well as color.MoreAs the color on the sapphire with natural heat only has improved in clarity as well as color.
What is the difference between heated and unheated gems?
You will get a more vibrant, saturated stone for your budget if you choose a heated sapphire. Most heated sapphires are eye-clean, with no inclusions visible to the naked eye. Unheated sapphires will have whatever inclusions were naturally created within them.
What does it mean when a bead is heated?
According to AGTA, a gemstone is considered heated when heat is used to create a change in color, clarity and/or phenomena.
What does it mean when a gemstone is unheated?
Unheated sapphires and untreated sapphires are one and the same as no treatment can be applied to a sapphire without the help of heat treatment. Unheated sapphires mean the sapphire is natural and it has not been enhanced by any form of heat treatment or any other treatment.
What happens to precious stones in fire?
They will gradually rise in temperature and reach a white heat. Then, the diamonds will burn uninterruptedly with a pale-blue flame, even after the removal of the oxygen heat source. The diamond crystals will gradually decrease in size and finally disappear.
What does heating a gemstone do?
Heating can also cause recrystallization of the silk inclusions to make them more prominent which allows the gemstone to have stronger asterism (a reflecting star effect).
Who is the author of Gem Treatments?
An Introduction to Gem Treatments. Robert Weldon. As a consumer, you will regularly encounter in the marketplace gems that have been treated to change their appearance. A topic that often comes up is whether a particular gemstone is or isn’t treated. In a sense, humans alter all gem materials after they are found in the earth in order ...
What is the chemical used to alter / reduce a component of, or the entire color, of a por?
Bleaching. – a chemical used to alter / reduce a component of, or the entire color, of a porous gem. Some gemstones are bleached and then dyed, a form of “combination treatment.”. 1. The most commonly encountered bleached gems include:
What is topaz coated with?
Topaz – Some colorless topaz is coated with metal oxides to create the appearance of a variety of different colors. In the past, such treatments were often described as a form of “diffusion” of a chemical into the surface of the gemstone, but this was a misnomer since in most cases the added color was confined to the surface of the gemstone.
Why do people alter gemstones?
In a sense, humans alter all gem materials after they are found in the earth in order to prepare them for use in jewelry. Natural gem crystals are transformed from their rough crystallographic form into the shapes, outlines, and degrees of polish in the gemstones that we appreciate and wear in jewelry.
What is surface coating?
– altering a gem’s appearance by applying a coloring agent like paint to the back surfaces of gems (a treatment known as “backing”), or paint applied as a coating to all or a portion of a gemstone’s surface with the effect of altering the color . 1.
How do diamonds change color?
Heating diamonds at high pressures and high temperatures can remove or lessen their brownish coloration so the gem becomes colorless. Other types of diamonds may be transformed from brown to yellow, orangy yellow and yellowish green, or to blue colors by this process.
What is the most common treatment for gems?
Heat treatment is the most common treatment and without heat treatment the availability of fine gems would be significantly less. With less gems prices would be dramatically higher only available to the rich. This is the reason untreated gems often command 30% to 50% higher prices.
Why is heat used in gemstones?
Why Heat Treatment is Used. Heat treatment is most commonly used to alter color but is also used to increase clarity. Rubies and sapphire can require significantly higher temperature to alter color and change clarity. Heating is used to either lighten, darken or alter the color of a gem. Amethyst is heated to lighten its color.
What temperature does tanzanite get heated to?
Tanzanite is heated to around 1000 degrees Fahrenheit. Tanzanite is a trichroic gem with blue, violet and yellow colors which in the rough appears as a color known in the trade as "diesel". If you look into a can of diesel fuel this is what fine tanzanite rough looks like, a brownish bluish red color. Upon heating the gem is left ...
What is the best way to lighten a gem?
Heating is used to either lighten, darken or alter the color of a gem. Amethyst is heated to lighten its color. Heat a little more and some sources of amethyst will alter color from deep purple to orange colored citrine. Uraguay is a good example.
How to change Geuda to blue?
Grey silky material known as Geuda can be changed to blue by heating. Not only do the rutile needles that cause the cloudiness disappear, these needles are also the blue coloring agent , titanium, that now upon heating produces a blue clear gem sapphire. Ruby heating alters color and improves clarity.
Is Ruby a natural gem?
The price adjustment for natural gems is based on our ability to identify the treatment which sometimes is quite difficult and beyond most jewelers abilities. Ruby is highly valued for being natural and can command more that 50% greater value than a similar treated gem.
Does heating alter ruby?
The heating may also alter cracks in the ruby by formation of ruby in the cracks due to very high heating close to the melt temperature of aluminum oxide. Emerald, garnet, peridot, chrome tourmaline, opals, alexandrite, ametrine, heliodore, kunzite, zoltanite and most spinels are not typically heat treated.
What is heat treated gemstone?
Heat Treated. Gemstone treatments have been used across cultures for centuries and are a common practice to bring out the best characteristics of a stone. Unpack the meaning behind heat treatment, learn the difference between enhanced and natural, and uncover the most commonly heat treated gemstones.
Why do gemstones need heat treatment?
In fact, most colored gemstones in the market have undergone heat treatment as a way to improve the stone’s color —and in cases like sapphire, clarity. Gemstone heat treatment is considered to be a stable, durable, and permanent treatment. In this post, we will answer all of your questions regarding heat treated gemstones.
What does heat do to a Ruby?
Additionally, heat treatment removes minute needle-like inclusions—known as silk—that causes the Ruby to be lighter in tone or more opaque.
What is the most well known gemstone that is radiated?
This is usually followed by heating the gemstone to maintain the ideal color. Blue Topaz is one of the most well-known gemstones that's radiated.
What is heat treatment?
Heat Treatment is a gemstone’s exposure to high temperatures that alters the color and increases the clarity. Specifically, heating is used to lighten, darken or enrich the color. Without heat treated gemstones, fine gems’ availability in the most desirable colors would be scarce. The price of the gemstone would also significantly increase.
Does heated sapphire make it transparent?
Similar to the Ruby, heating has potential to remove the silk inclusions and make the Sapphire more transparent. It can also recrystalize to make the inclusions more prominent for a star-like effect. Interestingly, heated Sapphire is darker in color.
Is aquamarine a heat treated gemstone?
The Aquamarine is surprisingly one of the most common heat treated gemstones. Its natural form takes on more of a green tint. If the Aquamarine does not heat underground, enhanced treatment is the next best option. Heat in a controlled environment removes the greenish color and produces a prominent blue presence.
What gemstones are heat treated?
A methyst, citrine, ametrine, aquamarine, tourmaline, topaz, light green tourmaline, sapphire, ruby, tanzanite, and blue zircon are gemstones that are typically color-enhanced by heat treatment.
What does heat do to gemstones?
High heat, such as that from a charcoal fire, can make a bland looking gemstone change its color into something spectacular.
How to tell if a stone has not been treated?
It is usually more difficult to find out if a stone has not been treated than if it has. Unadulterated stones can be harder to verify. However, there are some clues that can help. For example, gemologists can examine the inner workings of the stone and study the inclusions for signs of heat treatment. For example, if the stone has been treated, tiny inclusions such as small crystals will melt during the heat treatment process. A gemologist can easily see this using a microscope. An absence of such evidence could suggest an untreated stone.
What sapphires turn blue?
The same can apply to a type of sapphire known as gouda sapphire. These milky white sapphires turn blue, and account for many of the quality sapphires on today's market. D etection of heat and diffusion treatment is possible because these treatments modify natural inclusions.
What is heat treatment?
Heat treatment is considered to be a natural type of enhancement as it is a continuation of the processes that occur in the earth when the stone was originally formed. During treatment, the stone is heated to very high temperatures (approximately 1600 Celsius) causing inclusions, chemical elements, and other impurities to reform themselves and change the color of the stone. This color change may result in the stone being darker, lighter, more intense or of a different color. An example of this is the dissolving of rutile silk inclusions in blue sapphires, which improves both clarity and color. This heat treatment is permanent and irreversible.
What stone is more commonly heated?
Here is a full list of the more commonly heated stones and how heat treatment enhances them. Amethyst - lightens the color and will change the color of pale amethyst to "yellow" that will be sold as citrine. Aquamarine - removes the greenish undertones that are common in this stone to produce a more blue stone.
Can a gemologist see if a stone has been treated?
A gemologist can easily see this using a microscope. An absence of such evidence could suggest an untreated stone.
How do humans treat gemstones?
Humans have been enhancing and treating gemstones for centuries. This article explores the two of the most common methods used – Heating and Irradiation.
What gemstones are heated?
Some of the more commonly heated gemstones and the impact of heat upon them are: Amber : Gentle heating oxidizes and darkens Amber . Some Amber also contains gas bubbles that can make it appear cloudy. The bubbles can be removed by slow heating, generally whilst immersed in rape or linseed oil.
What happens when you heat rubies?
Heat causes structural changes in “silk” inclusions in ruby and sapphire. The rutile which forms the silk dissolves into the stone at high temperature (usually around 1800 degrees centigrade). Leaving a more transparent and therefore more beautiful gemstone. A large percentage of ruby and sapphire on the market today is heated and it is a fairly routine treatment. Unheated rubies and sapphires will contain microscopic rutile needles or tiny gas bubbles in pockets of liquid which are evidence that laboratories can use to guarantee that these stones have not been heated. If these gems are the finest color they will command premium prices due to their extreme rarity.
What is the process of changing a gemstone's color?
Irradiation is the process of using electromagnetic radiation to alter a gem’s color. Irradiation has been with us since the early 1900’s when scientists like Bordas and Crookes used radium salts to change blue sapphires and diamonds green. In today’s world, irradiation is routinely used to color a number of gemstones.
How does irradiation change the color of a gemstone?
The process by which irradiation changes color is fairly straightforward. Radiation causes electrons to be knocked off some atoms, leaving them free to be absorbed by others. This has the effect of creating “color centers” which in turn alter the light-absorbing pattern of the gem stone and by extension its color.
What is the oldest treatment?
Heating. This is a treatment that has been used for centuries. It is one of the oldest and most common treatments. History tells us that people in India were heating dull yellow chalcedony to produce bright orange carnelian as early as 2000BC.
What causes silk to dissolve in sapphire?
Heat causes structural changes in “silk” inclusions in ruby and sapphire. The rutile which forms the silk dissolves into the stone at high temperature (usually around 1800 degrees centigrade). Leaving a more transparent and therefore more beautiful gemstone.
What are the treatments for gems?
Today, most gems are treated to improve appearance. Treatment processes can consist of heat, irradiation, dyeing, oiling, or other processes. Detection of these treatments may be easy to nearly impossible. Treatments should always be disclosed to the consumer. The following are the most common treatments that are observed in the gem trade.
What is the most common method of treating gems?
Heating. The heat treatment of gems is the most common treatment technique used on gems. Reference to heat treatment of gems is found in gemological literature dating back thousands of years. However, widespread use started in the 20 th century. This treatment is usually detectable in many gems.
What is the purpose of oiling a gemstone?
The purpose is to diminish the visibly of fractures and thus improve transparency in the stone. The treatment is usually not permanent.
What is clarity enhancement?
Clarity enhancement/Fracture filling refers to the filling of surface breaking fractures or fissures with colorless glass, resin or similar substance. This process is done to improve durability, color and transparency.
What is a gemstone treatment?
Treatment refers to any process other than cutting and polishing that improves the appearance of the color or clarity, or that are used to alter the appearance (color, clarity or phenomena), durability, value, or supply of a gemstone. Today, most gems are treated to improve appearance. Treatment processes can consist of heat, ...
What is heat treatment on ruby?
This treatment typically occurs in ruby and sapphire during the heat treatment with flux components melting into and solidifying on the surface reaching fractures of the stone. In many cases this would improve the clarity by “healing” the fractures.
What is dyeing gemstones?
Dyeing refers to one of the oldest treatments recorded. The treatment involves the introduction of a coloring agent into a gemstone to give it a new color, intensify an existing color or improve color uniformity.
What is a gem coating?
Gemstone coatings are a simple way to enhance color and luster. Learn about commonly coated gems, different coating techniques, and how to detect…
What gems are more prone to treatment than other stones?
Corundum gems receive more types of treatments than any other stones. Learn how to test rubies and sapphires for signs of these enhancements.
What is the trickiest gemstone to separate?
Two of the trickiest gemstone separations to make are scapolite from citrine and apatite from tourmaline . Learn some tips for distinguishing…
Do cut emeralds have clarity enhancements?
Almost all cut emeralds have had clarity enhancements. Learn how these emerald enhancements work, what substances are used, and how to detect…. Emerald Treatments and Alternatives. Emerald treatments, such as oiling, are very common.
What is heat treated gemstone?
Heat treating is usually done to change or enhance color in a gemstone. Some gemstones are also “created” through this process. Citrine for example is generally heat-treated smoky quartz or amethyst. It has an entirely different color or appearance prior to being heat treated.
What is gemstone treatment?
It has been cut or polished to bring out its sparkle and color. When we talk about gemstone treatments, though, we refer to treatments which enhance color or clarity.
What is the process of bleaching a gemstone?
Bleaching is a process that removes color from a gemstone. It is usually done in combination with dyeing. Gemstones which are commonly bleached include jadeite jade (to remove unwanted brown coloration), pearls, coral, chalcedony, and tiger’s eye. Some of these are only bleached to lighten their color.
What are coated gemstones?
Commonly coated gemstones include diamonds, topaz, coral, pearls, and quartz. Topaz, and quartz are typically coated to change their color completely. Mystic topaz is an example of a coated gemstone that is not found in nature.
What gemstones are dyed?
Many types of gemstones are dyed, including pearls, quartz, lapis lazuli, turquoise, and more. Quite often when you see a bright, unexpected color in a gemstone, you should suspect dyeing. If you have ever been to a rock shop and looked at the tumbled gemstones, odds are you have encountered a lot of cheaply dyed gems.
Why is it important to be aware of the treatments used on a gemstone?
There is another reason it is important to be aware of the treatments used on a gemstone. Cleaning and maintenance. Gemstones which have been treated cannot always be cared for using the same methods as untreated gemstones. You may very well have to use other cleaning techniques than you normally would, or risk damaging your gemstones.
What does it mean when a gemstone is cut?
Any gemstone you purchase that isn’t in its raw state has in a sense been enhanced by a jeweler. It has been cut or polished to bring out its sparkle and color.
