I went for a medical examination today, which I require for work. Whilst I was having the medical I asked the head doctor if they wouldn't mind a few rocks on the x-ray machine. I usually get a no, but today I waited patiently for the chief radiologist to arrive and he said yes! They did warn me that their old machine might not be powerful enough. It was one of those machines where you put a plate below the specimens (or limbs) and then shoot. I said let's give it a go and see what we get.
Now in radiology there are a lot of variables that will affect the outcome, so really it's no good taking my values and trying them out on a different machine with different x-ray generator, different distances, different film etc. You'll have to try it out with different values - what is clear is that it does work on a conventional (and out-dated) machine and that you must use different values to get the resolution. If too powerful then you won't see a lot, however you may be able to pick up otherwise unseen smaller bubbles. With less power then medium bubbles will not be seen and with insufficient power then no bubbles will be seen. What is clear is that tektites can easily be x-rayed. You must have similar sized pieces on a photographic plate. I had a small bubble australite and a large bubble philippinite. The large philippinite and bubble can be seen but the small australite is not visible - much lower power is required for small bodies.
So on this first visit (and there will be more after the amazing results) we took 5 images. As a brief introduction to x-rays, it is the kVp that controls the kinetic energy of the electrons accelerated in the x-ray tube. The kVp controls the "radiographic contrast" of the x-ray image (the black/whites) (Wikipedia).
Peak Kilovoltage (kVp)
Exposure Time (Seconds)
Too powerful (dark x-ray)
Generally too weak (bright tektites, perfect to see bubbles in medium sized pieces, but no bubbles seen on biggest specimen despite it containing a monster bubble!) Perfect for about 25 mm thickness of glass.
Too powerful (dark x-ray, but did allow small bubbles to be found in very large tektites). Perfect for finding small bubbles in 70-85 mm thickness of glass
Just about right for breadcrusts- pretty much the right power to clearly distinguish most bubbles.(Small bubbles in largest tektites not visible - too weak, too powerful for small australites). Perfect for seeing small bubbles in glass of around 50-60 mm thickness.
What was I looking for in the x-rays? Well it was a bit of a rush job throwing these specimens together in minutes and heading back to the medical centre so I did not get everything I wanted. A second visit is necessary! Anyway, these were the things I wanted to investigate 1) Just to see the large bubbles in a few of the pieces and see their sphericity and whether it was one bubble or a bubble complex. 2) To view bubble complexes in breadcrusts (gatherings of small bubbles in the centre - I was sure these existed). 3) To see if asymmetrical dumbbells typically contained large bubbles in the bulbous end.
Provisionally, and it was a small database, this is what I observed. 1) Bubbles were of a size predicted for the larger specimens. These were single large bubbles, not bubble complexes. These were spherical to slightly ellipsoidal. 2) Breadcrusts did indeed appear to have bubble complexes - a number of small bubbles gathered in the centre of the specimen. Furthermore, to my surprise the larger smooth spheres did not appear to contain bubble complexes. The ones I had considered to be solid contained a single small bubble, larger than those in the bubble complexes. 3) Asymmetrical dumbbells did not appear to typically contain large bubbles in the bulbous ends, although bubble complexes were noted (which, of course, will always be more prominent in the larger bulbous end) - the bulk of the large bulbous end was glass.
The images you see below are somewhat compromised by the scan quality. The actual x-rays are of much higher quality and you can pick out subtle changes not visible here. Nonetheless they give a good idea of what I observed. Note that the photographed specimen may be in a different orientation as I forgot the camera battery when I went to the x-ray!
ABOVE: (X-ray #2) A large bubble in philippinite PX1117098 which weighs 147.5g and has Anda-like sculpture. Has volume of 77 cm3, so should weigh 188.65g. Bubble size was estimated at 16.73 cm3 or 31.7 mm diameter bubble. In x-ray bubble is 32 mm diameter.
ABOVE: (X-ray #2) A large bubble in philippinite PX1117462 which weighs 167.4g and has Anda-like sculpture. Has volume of 101 ml - should weigh 247g. Estimated to have 32 ml bubble equivalent to 39.5 mm spherical diameter. In x-ray bubble is 40x46 mm and ellipsoidal.
ABOVE: (X-ray #2 - left & x-ray #4 - right) A large bubble in philippinite PB1111747 which weighs 658g and comes from Bicol. Has volume of 358 cm3, so should weigh 877g. Estimated to have bubble equivalent to 55.5 mm spherical diameter. In x-ray bubble is 57x59 mm and is very slightly ellipsoidal. Note that in the first image the bubble hardly shows up because the x-ray was not powerful enough. By increasing the 'power' the bubble becomes visible. If the power is increased too much the whole image will be black.
ABOVE: (X-ray #4 & x-ray #4 edited to grey) Four breadcrust Philippinites (PB1113477, PB1117085, PB1112747 & PB1113503). Not sure of the order they are in on the x-ray and on the photographic plate, although the same specimens, they may be in a different order. All specimens from Bicol and weigh 283.3g, 259.4g, 157.7g & 172.4g respectively. Note the bubble complexes in all of these specimens. Also note that the bright area is not the whole specimen (only the thickest part). The whole specimen extends out to the subtle changes in colour. This is the limitation of the scanned image. So, the bubbles, which are roughly 2-6mm diameter, are genuinely concentrated in the centre of the specimen.
ABOVE: (X-ray #3). Now this surprised me. I had one 658g sphere (middle) that I knew was hollow and two spheres I believed to be solid. On the left we have PB1117429, which is an 865.11g smooth sphere from Bicol. It contained a slightly off-centre ellipsoidal bubble measuring 16 x 14 mm. The middle specimen we have already examined. It is PB1111747 which weighs 658g and comes from Bicol. Has volume of 358 cm3, so should weigh 877g. Estimated to have bubble equivalent to 55.5 mm spherical diameter. In x-ray bubble is 57x59 mm and is very slightly ellipsoidal. The specimen on the right is PM1115009, which is a smooth sphere from Masbate weighing 694g. It contains a 13 mm diameter spherical bubble and possible a 2 mm bubble to the side. The red line is an approximation of the margin of the specimen - it is visible in the actual x-ray, but not in the scan. These bubbles were only visible in x-ray #1 and #3 which were relatively powerful. The high 'power' is needed to reveal the bubbles in the thickest (central) part of these large tektites, n\but inevitably leaves a poorly defined margin and smaller tektites do not show up at all on the plate. The discovery of these small bubbles in the large spheres is of interest. Compared to the smaller breadcrusts, which cooled quicker, bubble complexes do not appear to be present - instead a single larger bubble is formed.
ABOVE: (Top x-ray #2, Top middle x-ray #4, Bottom middle x-ray #4 edited) This x-ray is of PX1117458, which is an exceptionally large asymmetrical philippinite dumbbell weighing 588.86g and being 162mm in length. The top image shows nothing as the power is too weak to effectively penetrate the specimen. The second two x-ray images demonstrate a bubble complex in the bulbous end of the tektite, but notably not a single large bubble.
ABOVE: (X-ray #2). Indochinite IV1112437 is an asymmetrical dumbbell from Vietnam weighing 94g. It shows up well in the low power x-ray #2 because it is only 25 mm thick. Again this asymmetrical dumbbell has a bubble complex in the bulbous end, but not a single large bubble.
ABOVE: X-ray #1, 200 mAs, 80 kPv, 0.200 Seconds. This high power resulted in a very dark image. It did show bubbles in the largest of spheres, but not particularly well. Too powerful. Second part of this sheet not shown as it is dark! Actual plate does show more detail than you can make out on this scanned image.
ABOVE: X-ray #2, 100 mAs, 50 kPv, 0.500 Seconds. This low power was too weak for the large spheres from Bicol and did not even show the biggest of bubbles, but fine for the Indochinite dumbbells about 25 mm in thickness. Also worked for the medium sized Philippinites with very large bubbles, but did not show up small bubbles in medium sized breadcrusts. Below about 15-20 mm thickness it was too powerful to show up anything. Actual plate does show more detail than you can make out on this scanned image.
ABOVE: X-ray #3, 100 mAs, 70 kPv, 0.125 Seconds. This high power was too strong for most of the tektites, but just perfect for showing small bubbles in the largest of the Philippinite spheres around 70 mm plus in thickness. You can see one in the top right hand corner, but the image scanned very poorly. Actual plate does show more detail than you can make out on this scanned image. Second part of plate not shown as mainly black!
ABOVE: X-ray #4, 100 mAs, 60 kPv, 0.063 Seconds. This low/medium power was perfect for medium sized breadcrust-type spheres of around 50-60 mm thickness. It was too powerful for smaller bodies and not powerful enough to show small bubbles in the largest philippinite spheres. Actual plate does show more detail than you can make out on this scanned image.
ABOVE: X-ray #5, 100 mAs, 60 kPv, 0.063 Seconds. This low/medium power was perfect for medium sized breadcrust-type spheres of around 50-60 mm thickness. It was too powerful for smaller bodies and not powerful enough to show small bubbles in the largest philippinite spheres. Actual plate does show more detail than you can make out on this scanned image.
Hope you enjoyed this page - I am sure there will be more to come!