If you have read my previous blog posts or seen my videos’ regarding what determines the value of gemstones, country of origin is one of the most important criteria. Certain origin where the gemstone is mined from always commands a higher price due to its history, rarity, and perception they have with traders or gemstone buyers.
I recommend if you haven’t read my previous blog post regarding the 4Cs + OT (Color, Carat Weight, Clarity, Cut, Origin, and Treatment), do check our ruby comprehensive guide where I also “ranked the ruby origins” that the market perceives to be higher than others. You can see the blog post here: http://www.buygemstone.info/how-much-does-a-one-carat-ruby-cost-video/
For the other two big gemstones – sapphires and emeralds – I will be shortly making a comprehensive guide so stay tuned and I will update this blog post accordingly.
In this post, I will discuss the methods of ‘origin determination’ used by labs or gemologists to check where your ruby, sapphire, or emerald is originally from.
What data do labs need to determine ruby, sapphire, or emerald provenance or origin?
It might sound cliché but for any science to work, we need evidence, data, and proof to determine if our hypothesis is correct or not. This is the same for gemstone origin determination.
You can simply think of it this way if we want to check if our parents are our biological parents or not we can compare our DNA with our parents and see if it matches based on the DNA strands. We can take this one step further and compare our DNA with other people around the area to find out if we are related or not.
The same method works for gemstones as well. To make sure the gemstone is from a particular provenance or origin it is important for geologists to gather data and check particular mine characteristics and ‘genetic’ environment.
For a gemstone to form they need the correct environment and chemical composition. Therefore the mineralogical properties of the gemstone are like the DNA of a person. For a gemstone to form, a geologist needs to study:
- The nature of the host of rock
- The interaction between the host rock and neighboring rocks, so there can be an exchange of chemicals and fluids that help with the formation of particular gemstones. This interaction can either introduce or take away chemical components necessary or unwanted for the growth of a gemstone.
- The pressure and temperature conditions where the gemstone is formed
- The chemical component’s needed for crystal formation of the gemstone. These components tell us the composition and nature of solution/liquids that transport, dissolve or participate with gemstone’s crystal growth.
To make a gemstones origin database, labs need to gather authentic reference samples and relevant analytical data from mines around the world as reference collection so they can compare and see with the gemstone submitted.
What gemstone’s origin information do the labs gather?
Unlike human DNA where the Doctor can take a blood sample through pricking a needle or by other more invasive methods, labs cannot take a large sample of submitted gemstone through such destructive methods (what is the point in checking if they have to do that!).
Therefore they have to collect data using ‘non-destructive’ method or at least “quasi-non-destructive methods” like laser ablation method or LA-ICP-MS, which leaves a small crater of up to 200 microns in size on the surface of stone.
With the samples collected from various mines from around the world the gemologist and lab will check the following:
i) Type of inclusions – like solid inclusions, growth features or cavity fillings
ii) Spectral fingerprints collected using “UV-Vis-nIR – range.”
iii) Chemical fingerprinting which includes major, minor or other trace elements
iv) Optical properties like RI “refractive indices, birefringence
Also depending on the type of gemstones, these criteria can be important
v) Infrared characteristics
vi) Luminescence behavior
By collecting enough ‘data’ of a particular mine or origin the lab will then compare the submitted gemstone to their database which helps them narrow down if the gemstones fit with that ‘particular’ mine’ “genetic background” during the natural crystallization process.
Why is important to use big labs to determine origin compared to in-house gemologist or smaller labs?
As you can imagine by seeing the number of data points required to determine a gemstone origin it takes a lot of time and resources to collect all this information. Therefore the larger labs will definitely have an advantage over the smaller players as they will have the resources to gather, store and analyse the gemstones over the smaller labs or individual gemologists.
In fact, based on data collected the large labs have noticed that certain mines share similar characteristics which I have summarized in some examples below:
- Some blue sapphire mines in Sri Lanka or Madagascar are producing blue sapphires features which are usually seen in “Kashmir” sapphires source (considered the most premium blue sapphire mine).
- The original Kashmir sapphire and “Kashmir-like” sapphire from Sri Lanka or Madagascar have “dust bands, flake-like inclusions, and very similar spectral and chemical features.” One distinctive feature is that Kashmir blue sapphires have pargasite crystals, which is not found in the other mines.
- Brazil Paribas Tourmaline has similar copper-bearing characteristics to Mozambique or Nigeria copper-bearing stones.
- The difference is usually Brazil Paribas Tourmaline is more ‘intense’ color in smaller sizes and has fewer color ranges than Mozambique copper-bearing tourmaline.
- Misidentification of Vietnam ruby as ‘Burmese’ Ruby as both are grown in marble bearing environment. The reason for this is the lack of data gathered on Vietnamese rubies by the labs when they were first discovered and sold in the market.
- Ethiopian emeralds do have similar inclusions to Colombian emeralds
But please note that the above examples are not ‘the rule’ but are rare instances when two different mines have similar characteristics.
To tackle the above issues, the bigger labs have started investing in databases, algorithms, and sophisticated software which checks 10 to 50 criteria or data points to help determine the origin of the gemstone.
Glubelin calls this ‘holistic’ approach in determining gemstone origin in their article “A Holistic method to determining gem origin, September 2006 article.’
How can a gemologist tell where a particular gemstone is from without sending it to the lab?
A gemologist can however give an educated guess as to where the gemstone is from based on inclusions and past experience. However, this is more based on probability as again the only way to fully verify is to check all the multiple factors which only the big labs’ database will have.
Example of inclusions of Mozambique (unheated ruby) shown below:
Example of “trapiche inclusion” and hexagonal growth along the optic axis shown in this ruby (unheated), Myanmar (Burma) below:
However, there are some characteristics that we gemologists use to ‘make’ higher probability guess if the gemstone is from a particular mine or not.
I am listing below some useful resources one can use to check the typical inclusions of different mines around the world. Again I recommend using this as a ‘gemstone’ enthusiast guide and not a definite way in determining your gemstone’s origin.
- Ruby Inclusions: https://www.aigsthailand.com/viewgallery.aspx?catid=1&title=Inclusions%20in%20Ruby&Ins=1
- Sapphire Inclusions: https://www.aigsthailand.com/viewgallery.aspx?catid=2&title=Inclusions%20in%20Sapphire&Ins=1
- Emerald Inclusions: https://www.aigsthailand.com/viewgallery.aspx?catid=3&title=Inclusions%20in%20Emerald&Ins=1
- Ruby Inclusions: https://www.gia.edu/gems-gemology/winter-2017-inclusions-natural-synthetic-ruby
- Blue Sapphire Inclusions: https://www.gia.edu/gems-gemology/summer-2017-inclusions-sapphire
- Emerald Inclusions: https://www.gia.edu/gems-gemology/winter-2016-inclusions-natural-synthetic-treated-emerald
- General Inclusion gallery: http://gemresearch.ch/inclusion-gallery/
- Inclusions Gallery – http://www.lotusgemology.com/index.php/library/inclusion-gallery
- Other publication citation – http://www.lotusgemology.com/library/articles/324-hyperion-sources-literature-on-inclusions-in-gemstones
I hope from the information provided above, you will understand why it is important to send your gemstone to a lab if the ‘origin’ is important for you.
Again based on my personal opinion it is more important to know the correct origin of some gemstones than others as they can either make the gemstone value go up or down dramatically.
Examples of getting origin correct in gemstones like
- Burma origin ruby, sapphire, or spinel
- Kashmir origin Blue Sapphires
- Brazil Paribas Tourmaline
- Colombian emeralds
With the above gemstones, I do recommend getting it certified from the bigger labs that have sophisticated resources to gather the data, have collected large databases, and have software that takes into account all these different factors.
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