The following is a brief study using microscopic imagery regarding a pink tourmaline specimen from AJS Gems that was acquired some time ago. This was originally documented as a study of 3 tourmalines; most of which were acquired from AJS Gems. There will be a 4th study conducted in a like manner at a later time to include another specimen. A more detailed study or addendum to this might be published at a later date perhaps.
This following images depict a 4.16 carat pink tourmaline, and it was disclosed as being from Nigeria and unheated. The very strong and intense pink colors have been said to originate from Nigeria, and don’t need heating as a result. There is an absence of orange undertones, but in certain lighting conditions, you can see more or less of it. It doesn’t have the orange color shift property that a Brazilian specimen from acquired from AJS Gems as well. I found all sorts of interesting artifacts in this particular tourmaline.
These images are uncompressed and unedited with the exception of green elliptical shapes to draw your attention to certain things that I thought were of interest. Other than the interpolation for resizing with the microscope software, no revisions have been made. Note that the blue background is actually a white napkin, so the colors for some reason are off a bit. I don’t have any software to color correct things anymore since my OS upgrade-otherwise I’d illustrate both the original and color corrected versions. Unless otherwise specified, the only light source being used is the LED light source from the microscope used. No ambient light was present at the time these images were obtained; a darkroom type condition was used for the study of this particular specimen.
Under a polariscope, and 20x magnification, there is evidence of a pink to orange pleochroism without the filters crossed over the diffused light source. With the polarizing filters crossed, there is evidence of double refraction consistent with tourmalines. I could not obtain an accurate optic sign and character with my chonoscope. Then again, I suspect this is due to the scope itself as my particular one is a pain to work with. I did see some hint of yellow towards the outside perimeter of where the optic character would be, thus suggesting it’s negative. Tourmalines for the most part are uni-axial negative with some exceptions.
Additionally, when I placed the stone directly over the bottom plate, I did see a lot lighter color and one portion of some growth rings. They seemed to be more or less linear with minimal delineation before an arc. They didn’t appear to be completely curvilinear like you would find in a synthetic stone. This region was between the bottom quarter and third of the stone in which these were observed with diffused polarized light. There was evidence of pink color zoning much like you might see in a Ceylon sapphire of some color, and the zoning appeared to be consistent with some other smaller specimens I examined under a loupe under incandescent lighting. This zoning was isolated, and the stone in it’s entirety appeared to be anisotropic through and through with crossed and uncrossed polars. I wasn’t able to obtain imagery of this zoning due to limitations of ergonomic design of the equipment being used, but I have found it in another tourmaline specimen. That imagery will be published at a later date.
This was originally observed with some solid inclusions near the top left region of this image adjacent to each other at 30x that illustrate some misshapen inclusions. However, further examination of this image shows what looks like a terminal end on 2 crystals side by side. These appear to be in tact. Note the reflection off the faces of the one terminal end. These 2 are circled in green. This misshapen part could suggest thermal enhancement or some other thermal event that occurred naturally. However, the terminal ends suggest an absence of thermal enhancements.
This is also at 30x. You can see what appears to be a solid single phase inclusion with in tact axial ends. There is nothing that suggests decomposition of any kind from this vantage point.
This is at 32x. We can see the reflection of the previous crystal inclusion, and we can see what appears to be an axial end of another single phase inclusion. This appears to be another crystal that is intact. The reflection of the light doesn’t match the facet pattern, nor does the shading from the light source of the microscope. These inclusions are again circled in green.
This was obtained at 40x. We can see the lower crystal better, and it appears to be in tact, and more or less matching the color of the host crystal. We can see the reflection of another suspect crystal on the opposing side. Color level adjusting reveals a hex shaped crystal, but we see the reflection only here that is not in line with the pavilion faceting. Additionally, the scorpion shaped inclusion seemed highly unusual, and unknown. Upon further study and other imagery, it appears that that inclusion is a layer of overlapping fields of plogophite inclusions (micas).
This is what appears to be a rectangular prism like inlcusion near the pavillion. This is at the same magnification as the previous illustration. It is worthy to note that there is a short needle like inclusion near this crystal. There have been other things resembling growth tubes elsewhere, but they are very small, short, clear, hollow and not reaching the surface. I point this out due to the recent concerns from not just myself but other entities that have pointed these things out with tourmalines. There is nothing suspect with this particular one of like kind regarding surface reaching inclusions.
This is an alternate view of the previous inclusions. The stone was re-oriented along with the scope to just happen to catch the reflections of several solid inclusions.
This is at 45x. We can see at least a terminal end near the NW corner of the culet. If you noticed this scorpion shaped inclusions appear to be discoid shaped inclusions. This appears to be a cluster of these artifacts in one area. There are other very short needle or tube like inclusions being in a more or less laminar direction through out.
This is at 50x. We can see what appears to be 2 adjancet crystals with terminal ends near the top, The far left and center illustrates another terminal end of a crystal we’ve already seen before. This is just another end. The bottom circled area illustrates a trapezoidal type of inclusion that doesn’t match the facet pattern. These have very defined edges, thus suggesting a lack of chemical decomposition from heat.
This is the stone at 180x. We can see tiny little single phase inclusions scattered about. This is something more or less common in this specimen. There is no readily obvious relation to these microscopic crystals with regards to any other inclusion. They are perhaps plogophites that were introduced metamorphically during the formation of the host. Plogophites are a group of minerals more commonly known as mica’s, and they contain some of the same elements as tourmalines. Pending the conditions, you could natrually have either occur with the same group of elements. It has been documented by the GIA amongst other sources that Nigerian tourmalines do contain mica’s.
This is a solid rectangular prism shaped solid. This was obtained at 220x. We can see the facet doubling as well as some smaller solid inclusions. The end of this appears to be like the tip of a chisel, and other parts appear to be clear in color. The light is reflecting off parts of the one face in this image, but this is a very small inclusion.
When viewing the culet or vicinity at ~219x, we can see this solid inclusion there.
This was obtained near 220x. There is what appears to be a doubling of various solid crystals, and a gas nebula like field. If you look past the gradient, you can see some smaller single phase crystals dispersing from this field. I theorize that perhaps this is a field of micas of some kind. Micas tend to reflect a lot of difussed light, and they can reflect a range of colors. This appears to be a more or less isolated artifact, and it doesn’t appear elsewhere in the stone.
From the pavilion view, note the green circled area. In other attempts, this area appeared to be a blurry cloud. When I was able to get a better focus on this, this looks very much like a fingerprint inclusion. You typically see these in certain Thai rubies, certain blue sapphires, and one Asian lab illustrates something like this with a new find of Tanzania rubies. This however appears to be a naturally healed fracture, and the inclusion is flat for the most part. This was obtained at ~49x.
These were obtained at 170x. These are variant views of what appeared to be discoid type inclusions. These appear in a near fingerprint like pattern, except these are not connected artifacts. They simple live in a discoid arrangement that has been distored in shape. This is simply a field of very small crystal inclusions. There are various fields of like inclusions through out, but this one was the most easily recognizable discoidal shaped field.
I have documented discoid type artifacts in other unheated stones, however the presence of a discoid that is perfect or more uniform in it’s curvature would suggest thermal enhancement after being mined. However, the irregularities here coupled with other artifacts suggest that some geological event caused a fast heating process, and after time the crystal continued to evolve. Therefore, the discoid we see is evident of a thermal event in my opinion than it is an enhancement by man.
-joe
NOTE: This is a revised version for layout purposes. No content was changed.
April 28th, 2009 at 3:32 am
Joe is a long time customer of ajsgems.com and does his own independent gemology research in his spare time. He’s a true gem lover….
Arnold S.
http://www.ajsgems.com
April 28th, 2009 at 1:14 pm
Thanks. It’s a true honor to be able to contribute to your blog in the manner I am in which you’ve allowed me to. I look forward to providing additional contributions of my own independent research.