So my wife had her engagement ring worked on recently as it had lost a few of it's itty bitty diamonds that surround the sapphire in the middle. While discussing the service work, the jeweler told her that the sapphire in the ring looked more like a Tanzanite then a Sapphire due to a large amount of scratching and other damage on the stone. He suggested she get it analyzed in a spectrometer to know for sure. When she came home and told me this I of course was less then happy because the ring was sold to me as a Sapphire. Before anyone says "that's what you get you cheap bastard" she picked it out from this place that carried antique jewelry online and I bought it without her knowledge to surprise her when I proposed a few years back. After she told me the news I performed all the known do-it-yourself tests on the stone to see if I could determine if it was a Sapphire or not. The tests were inconclusive. So I decided to investigate these scratches and gouges myself. Not having a microscope, reversed lens stacking is my only means of seeing into the sub-macro world. Here's what I found.
Just for everyone's knowledge, all the pictures below were subject to minimal post processing. Auto Levels, contrast adjust, re-size and finally minimal sharpening.
Here's a the ring at close to 1:1 for comparison. I used a Tamron Adaptall-2 90mm 2.8 macro at f11.
Roughly 1.80:1. This was the first stack using both my macro lenses stacked. I was actually the least pleased with the results from this combination. Tamron AD2 90mm 2.8 with Sigma 50mm 2.8 reversed. Both lenses were set to f4 for this shot. I tried only setting the aperture of the Sigma to f5.6, but the vegnetting was very pronounced, so I compromised by setting both lenses to f4.
Roughly 3.75:1. This ones is using the same Tamron 90mm but wide open this time with a Miranda (Cosina, Vivitar) 24mm f2.8 reversed and set to f5.6.
Roughly 5.63:1. This was taken using a Pentax-A 135mm f2.8 wide open with the same Miranda 24mm reversed and set to f8.
Roughly 8.33:1. Now we start getting really close. Taken using an old M42 Auto Mamiya Sekor 200mm f3.5 wide open with the same Miranda 24mm reversed and set to f8. The flare spot you see is probably a result of the older singles coated optics of the Mamiya Sekor. Regardless, resolution held up nicely.
Roughly 16.67:1. This was by far the hardest shot to take and is the only keeper out of about 20 shots. It probably could have been sharper, but it's hard to get sharp results at that magnification when there are two little boys chasing each other around the house sending vibrations through the floor system. Taken using a Tokina SD 400mm f5.6 with the same Miranda 24mm reversed and set to f5.6.
I'm still not sure if it's a Sapphire or a Tanzanite. Assuming this really is an antique stone and setting, it's possible the the sapphire was damaged when purchased and we just haven't noticed until told. I guess I'm just going to have to get it spectrally analyzed to know for sure.