Hey. I bought this gemstone as a tourmaline, 1ct blue gemstone which shows dychorism- yellow from one angle blue from another. It has 1.76 something RI and the birefringence doesn’t really move, at least I couldn’t see it moving, SG I didn’t measure. Let’s say it’s very probably a sapphire and under microscope I can see these bubbles. Are those inclusions bubbles or something else? is it a natural stone?
How many positions did you take the RI measurements at? Since the stone is showing pleochroic colors at different viewing angles, birefringence should be observable in the RI test.
Both Tourmaline and Sapphire typically show birefringence.
Do you have a dichroscope?
The inclusions are hard to distinguish in the images. The curved group of (large bubble?) inclusions in the image facing the culet/pavilion facets are suspicious. Bubbles are not normally found in natural sapphire but can be seen in some Lab grown corundum.
When observing the stone in the microscope, can you see curved or straight growth lines? How about color zoning?
Hey, thanks for the answer!
I made more RI measurements and it moves just a little bit on 1.76 but a little just but I can’t say in which direction, my RI machine is pretty cheap. I don’t have a dichroscope. Those bubbles are suspicious, that’s why I asked. there is color zoning yellow - blue and I can’t see any curved or straight growth lines. What is your differential diagnosis here? Those bubbles are not structured or something. with the loupe the gemstone is clean, I can only see that bubble that is bigger.
Hi Tudor,
Now that you mentioned it, in some of the images, I can see yellow and blue colorations in different facets. I am curious how these color zones look in an immersion test.
Are the color bands seen together when looking through a specific direction or are they seen separately when looking from different angles? An immersion test may reveal some interesting clues.
I started to look into some additional examples of inclusions that look similar to those in the third image. They might not be bubbles, as they seem to have some angular features (mirrored in the reflection of each one). Although, these could be optical illusions as it is not easy to distinguish them clearly.
Have you found or seen this site → Hyperion Inclusion search by Lotus Gemology?
There is a very large database of images of various inclusions, selectable using gem group/species and additional keywords such as “Natural, Heat treatment, etc.”
Due to copyright and intellectual property clauses, we cannot post or link the images here without explicit written permission.
If you use the following keywords or menu selections: Natural Sapphire • Sri Lanka (Ceylon) • Enhancements: None Detected it should bring up about 14 images. Towards the end of the list, is one that has similar shaped negative crystal inclusions. I would be curious if you see similar shapes in your stone.
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Hello Troy,
I don’t understand what you mean by the bands being together or separately. I am pretty new in gemology and I am really beginner at looking at a gemstone. Thank you for the website, it’s really helpful <3 Made some more photos of the color zoning.
Regarding the negative shaped crystals, maybe yeah they look like them.
Thnx for helping me. It’s really helpful to have someone near you when you’re exploring this world
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Hi Tudor,
Thank you for posting more images! They provide some additional details.
I am also a gemology student, so I apologize for any confusion I generate. Bare with me as I attempt to describe things and hopefully others will correct me and/or point out things I miss. 
Lets start with this image: 2024_1215_122740_007: If you zoom in slightly, you can start to see blue color bands that seem to be in straight lines. Color bands develop in the same direction as the crystal grows. This indicates one of the physical axes of the crystal structure.
When they are not curved or wavy, it is a good indication the stone is likely natural, but more information is needed to determine that.
It is possible the yellow hue is also from color bands, but usually on one of the other physical axis planes. This is what I was referring to regarding different directions (view points) or orientations of the color band lines.
The yellow could also be the base hue for the entire stone and the blue bands simply generate a stronger saturation for those patches (zones) with a blueish color. There could be some areas that are tinted with a greenish hue where the two zones merge or overlap based on the viewing angle. Looking at the stone from different directions, can show whether or not this is the case.
Here is a good article on crystal structures.
The immersion test, I mentioned previously, is a great way to see all kinds of features including color bands and growth lines. Water is a great fluid to start with but is definitely not the best for corundum and tourmaline. The test works better using a liquid that has a similar RI value to the stone. One of the forum’s members, @royjohn, has mentioned Benzyl Benzoate in various conversations. Benzyl is non-intrusive and is less likely to disturb or contribute to any treatments like dyes and/or oils that might be present. There are other household liquids that can be used as well.
Another interesting feature is in image 2024_1215_123034_012. The dark blob in the stone doesn’t seem to be visible in any other image you have posted. I am not sure what that is. Can you see it from other angles?
We can go over the RI tests you did to try and figure out why the birefringence is not vey observable. As you mentioned your refractometer may be a factor to consider, but there are some hints and tips to help even the most economical instrument perform as intended.
I know this seems to be a lot of information to throw your way, but I think it will help.
Cheers!
Troy
Hey Troy, I understand now what you mean with the bands. They’re not curved or wavy. By immersing in water I can only see more transparent the part where the yellow zone is, but I can’t see any bands. I don’t have other liquids for now.
The dark blob in the ston can be visible only from that angle. It’s weird. I am working tomorrow till late , I’m a doctor also so maybe I could get some pictures the day after. I could try also do another RI test. Thnx for the help!
RI is closer to corundum than tourmaline. check specific gravity. Corundum stones are much denser that tourmalines at 4… looks more like a synthetic sapphire than a natural, tourmalines are not synthesized for the market…lots of bubbles make it look synthetic, (bubble withs two phases, rarely three can occur in natural, but they are rare…can’t tell from the pix about the color banding very well… curved or straight?.. curved would tend toward verneille process synthetics (cheapest)…
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Looks natural to me. Its got inclusions.
Inclusion bubbles. Thats a natural sapphire. Looks like a party sapphire.
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Hi GuineaPig,
Welcome to the forum! The stone could certainly be called a “parti sapphire” if it is the mineral corundum. 
Few more tests should help narrow down the possible group/species.
Cheers!
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I agree that a SG test would help. Using dark-field imaging could have a better chance to see the growth lines.
UV light (LW and SW) would help.
The large inclusions could be negative crystal inclusions… (possibly a seed crystal if it is lab-grown).
There is still the question of the stone being sold as a tourmaline, if it is sapphire? That would be a mistake on the seller for sure. A lab-grown sapphire could fall into the same the price range of tourmaline, though. There are a few facets with uneven meet points. That would lower the cut grade.
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hello, I don’t have the tools for SG. I will do RI again, dark Field and I will buy one UV light torch. It will take some time I am also a medical doctor.
I think it’s a sapphire but not sure if syntetic or natural.
It was sold as a tourmaline but the guy was selling lots of gemstones for 10€ that he didn’t check. He thought from the color only that was a tourmaline. I also bought one more, I will also need help with that 
It isn’t about money, it’s just that I learn gemology
Thnx for the answers
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I myself am a retired medical doctor, Jewerly making was a hobby for me. I’m studying geochemistry at the present time as another hobby… so far as Specific Gravity is concerned, you can ask Roy John how to make your own set up… SpG is simply the weight of a stone in water versus the weight of the stone in air… all it is, is Archimedes Priniciple… you do need a sensitive balance that weighs into milligrams or tenths of milligram depending on the size of the stone…corundum is very dense… SpG of around 4, much heavier than tourmaline… just from the looks of the pictures, I would vote for synthetic sapphire… synthetic tourmalines are not on the market… they have been synthesized for research purposes but not commercially. SpG wll definitively tell you whether it’s tourmaline versus something much heavier, such as corundum. There are too many bubbles and color banding in the pictures, so that if it is corundum, it would most likely been synthesized by the Verneuille process. This would be especially true if the color bands were curved. Natural stones do have growth banding, rarely one or two bubbles that are 2 phase… bubble inclusions in natural sapphires usually indicate an igenous origin.
You could also take it to a local jeweler for their opinion… that might be the easiest option… someone you know could inspect it and do it for free… no need for an appraisal.
It’s safe to say it’s corrundum. I can see only 2 bubbles inside, the other ones parallel are an optical illusion.
Also I’ve got the growth bands and they look pretty straight. I think it’s a natural but I will come back when I get the other measurements. It will take some time for sure.
Hey there. So in that day when I bought that sapphire with 10$, the guy had another box full of gemstones with 10$. I looked like 10 minutes and I found this violetish blue gemstone. I asked him he said it’s an aquamarine but I don’t think so… it has a 1.69 RI and when I rotate the polarising lens it moves to 1.698 approx. almost 1.7. On the microscope it has only 2 discoid fractures on the table and no other inclusions. I am thinking about Tanzanite.
Hi Tudor,
Thanks for the responses and update. I understand your approach to learning gemology. I have also purchased some inexpensive stones, that I thought were not really worthy for remarketing value, but worth the money spent, as a practical exercise in identification. 
Your original stone, might have an interesting discovery just waiting to be realized. Hopefully everyone agrees that the following is true:
- Both sapphire and tourmaline are doubly refractive: Uniaxial (-).
- Both have R.I. ranges that overlap.
- SpG for each is different, but there is a narrow margin gap between them.
Steve, (@StevenH26783) is right, a specific gravity test would help determine what group it is or is not.
You may have answered the question of whether it is natural or lab grown, since you have observed straight growth lines. 
: Natural
What remains is the extremely weak or lack of birefringence. Both tourmaline and sapphire should exhibit this. However, several papers/literature mention some tourmaline species can display singly refractive behavior, if the O-ray has been nearly or completely absorbed (plane-polarized light) 
I am still trying to understand what is meant by this.
Another stone also exhibits no birefringence and meets the RI range and similar SpG to tourmaline: Spinel
Heidi (@GuineaPig) had suggested it could be a parti-sapphire. Interestingly, all three stone types can show patched color zones (parti-colored). Spinel and Sapphire are more commonly seen with this than tourmaline.
I know I suggested doing a UV light test. But fundamentally, UV may not provide definitive clues. The SpG test will help and it seems a polariscope would be the best way to determine the optical sign.
Cheers!
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Thanks. Very interesting!
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