Ruby Treatment Guide – Unheated, Heated, Flux-Filled, Lead-Glass Rubies

Video explanation between unheated ruby vs lead glass-filled ruby (composite ruby):

The second video shows different ruby treatments under a microscope


Before buying any ruby it is important to know what type of treatment it has gone through.

Natural Rubies have different levels of treatment.

  • Natural (no treatment)
  • Heat Treatment to enhance color
  • Heat Flux Treatment to enhance color and clarity
  • Lead-Glass filled Treatment to change characteristics of a ruby

The more treatment the ruby goes through the lower the price gets! 

The price can range from exceptionally expensive US$10,000+ per carat for unheated, natural rubies to US$5 per carat for lead-glass filled rubies. 

Glass-filled rubies have flooded the gem market from traditional retail stores, online websites to sellers on eBay.

Simply checking the authenticity of the certificate and understanding the ‘treatment’ section, you can save thousands of dollars.   This will also save you time and the harassment of getting scammed by the seller due to them not disclosing these facts to you.

I hope this guide will provide you with a basic understanding of the different types of ruby treatments.

I do want to emphasize that even if you read this guide, it does take years of experience seeing rubies to understand the different levels of treatments.

If there is any doubt about your purchase – “Even that slight 1% chance” – it is always best to recheck the stone from a reliable gemstone laboratory or trustworthy gem dealer.


Natural Ruby that are NOT heated or treated are quite easy to check.  You will only need to see through a microscope or gem loupe for natural or intact inclusions.

Natural Inclusions Are:

  • Intact, fine, needle-like Silk (rutile needles) intersecting at 60 degrees angle. In the same plane or other fine needles at near right angles.
  • Boehmite needles
  • Fingerprint inclusions
  • Angular, straight, or hexagonal growth zoning or banding
  • Straight, angular, and possible color zoning and color banding
  • Unaltered mineral inclusions, clear or opaque color, that might show angular faces
  • Intact two-phase inclusions

Below are some sample images of rubies with these characteristics. Please note that it does take some experience to check and verify if the ruby you are looking at is completely natural or not.

However, if you do have a great pair of eyes and can see these inclusions and NONE of the other inclusions described in the guide below, you can be sure that the ruby you have in hand is natural, unheated, and untreated, the rarest of all rubies!

Unheated Ruby - Intact and unaltered Calcite Crystals
Intact and unaltered Calcite Crystals. Photo courtesy from © Paolo Cerruti
Unheated Ruby - Natural Apatite Crystals
Natural Apatite Crystals. Photo courtesy of Photo © Richard W. Hughes
Ruby Treatment Image - Unheated Ruby - Another intact and unaltered calcite crystal and hexagonal color zoning seen within
Another intact and unaltered calcite crystal and hexagonal color zoning is seen within. Photo courtesy of Photo © Richard W. Hughes
Ruby Treatment Image - Unheated Ruby - Intact Silk inclusions
Intact Silk inclusions. Photo courtesy of Photo © Richard W. Hughes


Almost all rubies – 95% of rubies today – are heat-treated.  There are different types and levels of heat treatment in rubies that can be classified from very slight to quite extreme.

Distinguishing these levels of treatment can also affect the price of a ruby dramatically.

Heat treatment is used to either develop or intensify a ruby’s natural color.   Higher levels of heat treatments can also improve the clarity of a ruby by removing or reducing inclusions and making them less visible.

The way this works is quite technical and I will not be explaining it in this guide. But you get an idea of why people heat treats rubies.  They want an unattractive ruby to look a lot better, so it will be easier to sell.

Inclusions of “Normal Heat” Treatment Rubies Are: 

  • Discoid fractures with tension halos. It looks like disk-like fractures with lace-like outer healing rims. This is caused by expansion of natural crystal inclusions.
  • Burned or altered mineral inclusions. With rounded, often whitish, “cotton” like or snowball” appearances
  • Broken silk or partially “reabsorbed” rutile needles
  • Ruptured two-phase inclusions and negative crystals
  • Sintered surface areas, especially around the girdle

Prices for normal or slightly heated rubies are still not cheap.  Good ones can still cost upward of US$5,000 per carat.

However, before paying these high prices, PLEASE make sure the ruby which you are purchasing has not been subjected to newer or higher step treatments which are shown below.

This is because the price for higher treatment rubies can drop dramatically.


A good way to double-check if the ruby is what is stated is by asking your jeweler or gemstone wholesaler for a reliable certificate with the stone.

On a GRS certificate, it will state the ruby is only subject to H treatment, or H (a) is also acceptable.   GIA will classify normal heat treatment as ‘Heated.’

If it is written H(b) or below then you will know that the ruby has been subject to newer treatments and you should not pay the price for normal heat-treated ruby.  GIA will classify higher levels of treatments as Heated (‘Minor or Moderate or Significant’ Residue).

For all the GRS classification details, you can click on the following link:

Ruby Treatment Image - Heated Ruby - Discoid fractures with tension halos
Discoid fractures with tension halos. Notice the disk-like fractures with lace-like outer healing rims. Photo courtesy from © AGSL
Sapphire Treatment Image - Heated Sapphire Ruby - Though this image is not a ruby, the inclusions will look the same in normal heated ruby. This image shows discoid fracture with tension halos and burned, altered mineral inclusions (in the middle) with rounded "cotton" like or "snowball" look
Though this image is not a ruby, the inclusions will look the same as a normal heated ruby. This image shows discoid fracture with tension halos and burned, altered mineral inclusions (in the middle) with rounded “cotton” like or “snowball” look. Photo courtesy of © Alberto Scarani
Ruby Treatment Image - Heated Ruby - Dotted Rutile Silk and not straight intact lines proves the silk has been burned or the ruby has been heat treated.
Dotted Rutile Silk and not straight intact lines prove the silk has been burned or the ruby has been heat treated. Photo courtesy of Photo © Richard W. Hughes


The next more extreme level of treatment for rubies is called heated ‘flux-healed’ rubies.  On reliable certificate providers as stated above they will indicate these rubies as H(b) or ‘heated with residues.’

For this level of treatment, treaters add “foreign” material to the rubies by surrounding them with a flux-like material, which becomes molten at extremely high temperatures.

The dissolved flux will then fill the fractures and cavities from the open stone’s surface which will then solidify into a glass-like substance.

This process improves the apparent clarity of the ruby, but because the composition of these materials is not completely “natural,” the price for these rubies is substantially less.

The price is depended on how much residue is presented in the heated rubies.  Most labs do classify the amount of residue by stating it as minor, moderate, or significant residues.   For each level of treatment, the price will drop accordingly on average by almost 20% to 50% per carat.

Inclusions for Flux-Healed Rubies Are:

  • Flux inclusions are generally white and have glue or sticky look.  But, it might also appear near-colorless, whitish, brownish, or yellow to orange. PLEASE NOTE: Even though these inclusions indicate flux induced by the heat process. There are also flux-growth synthetic rubies which are man-made stones and NOT natural rubies. For more details please read our next post on synthetic rubies.
Glass-filled Composite Ruby - Flux Residue inclusions. Noticed the glue or sticky look
Flux Residue inclusions. Noticed the glue or sticky look — Photo courtesy of Photo © Richard W. Hughes


The most aggressive type of ruby treatment that has flooded the markets is called lead-glass-filled rubies.  The average prices for these rubies are usually US$ 5 per carat or less.

These stones are really not worth anything.  This is because, in their natural state, the rough would have been an ugly, highly included brown color, which would NOT have been saleable if not with the help of this treatment.

How it works is usually this “bad” looking ruby – If you can call it ruby – is mixed with acid to remove mineralized inclusions making the stone texture soft and weak like a sponge.

If you hold the stone in this state it will crumble into powder.  This material is then infused with leaded glass to give back the strength and apparent good looks.

For an average consumer, you would think this is a beautiful natural ruby, which I am getting in a cheap price or a good deal for.

The problem with this type of treatment is many as listed below:


These stones are not rubies anymore. It is a mixture of natural corundum and lead glass. Actually, most of these “rubies” have more lead glass in them.

Yet they are still being sold as natural rubies in major stores and/or some eBay or online dealers which makes this a major disclosure issue.

If the sellers actually disclose the treatments of these stones to their clients, the purchaser can then make a more informed decision on how much you should pay for this type of ruby.


As it is not purely corundum anymore, this ruby can get ruined immediately if you give it without informing the ring setter.  If the manufacturer torches the ring for resizing and it touches the stone with heat, it will crack.

If you re-plate your rhodium plate white gold ring it will destroy the stone.  For natural rubies, you don’t have to worry about any of the above issues.


Also, if you are not careful in wearing these “hybrid” rubies they will change over time.

For example, if you accidentally spill some lemon juice while eating, the stone will slowly decay in a few days.  Therefore, your supposedly “beautiful” stone, will now look like it was thrown from a high-rise building.

Therefore, if you are in the market buying rubies it is very important to find out and check for these types of rubies.

Inclusions for Lead-Glass Filled Rubies Are: 

  • Gas bubbles are sure indications of glass-filled rubies or synthetics.  Usually very easy to spot under a microscope or a loupe with dark light background.
  • Blue and Orange flash effect along with structural fractures when put under a black light. It is also a key indicator of lead-glass filled rubies

Again, the best way to find out if the stone you are buying is lead-glass-filled rubies is by either having a great pair of eyes and check for the signs above or getting the stone certified by a reliable lab.

GRS certificates will classify these rubies as “Hybrid” Ruby.  It will have the following comment “Heat-treated and filled with a foreign solid substance (including lead).  Special care when handling.

Also known as “Composite Ruby.”

Glass-filled Composite Ruby - Gas Bubble inclusion
Gas Bubble inclusion
Glass-filled Composite Ruby - Gas Bubble seen at the right side of the stone
Gas Bubble seen at the right side of the stone — Photo courtesy from © Wimon Manorotku
Glass-filled Composite Ruby - Blue and Orange flash effect along structural fractures
Blue and Orange flash effect along structural fractures — Photo courtesy from © Barbra Votaire

I hope the above guide is helpful. If you have any additional questions. Please feel free to provide your comments below or send me a message at
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27 thoughts on “Ruby Treatment Guide – Unheated, Heated, Flux-Filled, Lead-Glass Rubies”

    1. Shawn

      I have a 2.2carat untreated ruby with certificate. Just for the hell of it over the yeats i have been in several shops that buy colored stones. About 7. I would just bring in and say nothing about the cert. some said completely fake, some said minor heat treatment. Some said real and untreated but liw maybe just bad luck huh?

  1. lalit verma

    great source of knowledge please update on other gemstones

  2. Fatin

    wow this is such an informative article! Love the website learnt alot! Thanx

  3. shellxxxx

    well , ruby , emerald , let us see the sapphire too !


    Pretty nice post. I just stumbled upon your blog and wished to say that I have really enjoyed surfing around your blog posts.
    In any case I’ll be subscribing to your feed and I hope you write again very soon!

  5. MD Hoque

    Thank you for this nice elaborated explanation on the ruby. I found a natural heat treated ruby from a local jewelers store known by paramount jewelers. It has been really hard to make the decision. So the Ruby I am talking about is a natural heated Mozambique Ruby. Which has 1.78 ct and they are asking for $2200 with their own certifications. How should i approach this deal.
    Please guide me at your best possible way, your help will be really appreciated

    1. Hi MD Hoque,
      The way I will approach this deal is by first checking if paramount jewelers, who is providing the certification, has someone qualified to do so. Usually most established jewelry stores will have a graduate gemologist (from GIA preferable) in house who can verify if the ruby is natural & only heat treated. If there isn’t any qualified individual who can do this than you should ask if they can provide a third party certification just to make sure you know what ruby you are getting.
      “Heated” natural ruby is also a very broad definition and as you can see from this blog article there is different “levels” of heat treatment, which can affect the ruby price. Price from highest to lowest is 1) Normal Heat treatment 2) Heat treatment with flux residue inside the ruby 3) Heat treatment with chemically diffusion…. For each level downward, the price drops dramatically, so that is why it is important for you to understand when the certification states heat treatment to check and see “what type it is”.
      I wish you the best of luck with ruby purchase and do feel free to ask me any question anytime.
      Tarun Gupta, Graduate Gemologist (GIA)

  6. Vlad

    I am the president of the company, working and living in Cambodia. Since 2008 I have been working on Burmese rubies, have partnered with Mogok. Personally fly to purchase stones. I would like to bring to your attention rubies, sapphires, spinel only from Mogok and just not warm stones. Stones are in stock and on order.

    1. ANDREW

      Hello, what are your prices for rough rubies and sapphire (heated only-facetable- high quality)
      per ct ?
      Do you sell from cambodia? Do you have a contact tel number?
      Will appreciate if you can gave me please give me your best initial price
      as I am now looking to start .

  7. Jitendra vinayak ranalkar

    Best knowage..

  8. steve b.

    Hmm interesting. Please also say that Ruby is a ‘sapphire’ too, it’s just a red sapphire 🙂 Most people think ‘blue’ wwhen they hear ‘sapphire’, mostly prefer very deep, dark (but clear), blue.
    Also, since the best Ruby is harder to find than comparable diamond, and very rare, also that NO WAY is average person going to get natural heat Ruby at a few full carats. They won’t be at any chain jeweler s for sure! MOST rubies that look pink more than red are Thai rubies, and always considered far less valuable than African rubies which, ideally, should ‘glow’ blood/stop-light red rather than sparkle and NEVER have a brownish hue. Else they are probably red garnet, not ruby.
    Finally, unless person with expensive Ruby gem knows jewelers very well, NEVER to leave for cleaning with ANY jeweler and jeweler should ALWAYS clean rare gems such as these by appointment, IN FRONT OF customer WITHOUT BEING ASKED!! I had a relative who a friends family member once robbed by a very good jeweler-thief like that and she never, ever got over it and it was her word against the jeweler’s because she didn’t realise till much later that something ‘seemed wrong’ and this bad jeweler was counting on such trusts and getting away with it!!!!! The natural heat rubies grow increasingly rare and expensive, so it’s important people know this.

    1. Hi Steve,
      Thanks for your comment and you are correct by stating that by definition a ruby is a ‘red’ color sapphire. They both are in the same “corundum family” and therefore have the same toughness & hardness characteristics.
      In fact, sapphires come in all colors and it just depends on their chemical composition. Color ranges include blue, pink, yellow, green, purple, etc.
      Now regarding rubies being more ‘rare’ then diamonds, I completely agree with you in that statement and searching & sourcing a nice high quality ruby is not easy. I also agree with you that high quality ruby has been a good investment due to this rarity factor.
      However, your comment regarding African rubies being ‘higher’ priced in comparison to Thai rubies actually is not true at all. Yes, Thai rubies ‘generally’ are in darkish red color range, but as there aren’t any rubies being mined or produced from here anymore since the late 1980s, they are now very rare to find. Also, the most premium source of rubies are still Burmese rubies and they actually glow the most due to them having less iron in its composition which allows it to ‘fluoresce more’ in natural sunlight. There are of course beautiful Mozambique rubies but they are still a lot more affordable in comparison to a Thai or Burmese ruby as they more easily available due large production coming from that source.
      Tarun Gupta, Graduate Gemologist (GIA)

      1. Peter

        I have new discovered stones that we think could be rubies.May l request Waatsap number to send pictures.

  9. Dan

    Thank you for an extremely informative and well educated article. You have my thanks.

  10. i have a 3.98 cush cut all natural burmese ! any offers ?

  11. Shawn thompson

    I have bout 66.0 carat ruby I can send picture but I’m confused. I have oval hand cut untreated RUBY. RED&SLIGHTLY purple w/whitish streaks in it. It’s size color & being told such a variety of values. I only know sending to Swiss gemologist that it’s a ruby, but would that gemologist give me an impartial course of action as to where, how, which, if, or any opinion AS ITS FUTURE SHOULD TAKE. Mainly appreciative on understanding this subject.

  12. neeraj agrawal

    i was looking for the properties of natural and heated rubies as i deal in these stones.also nowadays labs are less reliable so i want to thank you a lot for such useful information which will make me improve my knowledge about the stones.

  13. Nena

    Would someone plese give me a phone number from president of the company’s in Cambodia I’m looking for natural Burmese ruby and sapphire, certified I have very bad experience from USA and India purchase 2 ruby from dishonest people state that is reall ruby and it was glass filed I was craying and not was able to return them,!
    And it as gifts to my daughters,

    1. Hi Nena,
      We only have one main office which is located in Bangkok, Thailand, though we can ship across the globe through FedEx with full insurance. Now regarding getting cheated in buying your ruby, I believe our blog does cover very important points which you should check before making your purchase to make sure you getting the genuine thing. Also, always do remember that the most important thing in buying gemstones is to make sure you dealing with someone who you can “trust” and the certificate received is from reliable third party lab.
      Best Regards,
      Tarun Gupta, Graduate Gemologist (GIA)

  14. Chase

    Thank you so much for this information. I recently purchased my first ruby for my favorite seller, who always informs if the stones are treated and includes pictures of the actual product, they even have a filter to separate fracture filled and flux healed stones from only heated ones, which is amazing. Im so happy to know my new 0.16 carat heated only ruby is still real!

  15. Nuha

    I have rough rubies, where can I heat it to improve the clarity and color.
    Thank you

  16. jewelry stores near me

    It’s natural ruby buying gifts.

  17. Soubhagya

    Indication of heat moderate residue in fracture, what the meaning of this

    1. It means the ruby has been treated with heat treatment to improve both its color & clarity. Classified as H (b) – Or heat treatment with flux residue. Slightly more aggressive treatment then just normal heat treatment, which only improves color.


      Tarun Gupta, GIA GG

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