Well, I've pretty much finished collecting spectra of three rubies. The first ruby, with a direct path through the stone half as thick as the second ruby, allows almost exactly 10 times more light intensity to reach the spectrometer. The third ruby allows about half the intensity of the first one. So one can compare spectra between stones pretty well.
mineral box 699, stone 1 (of 3)
corundum var. ruby
location: India
mass: 0.88 g
(click to see larger image)
mineral box 534
corundum var. ruby
location: Burma
mass: 2.00 g
(click to see larger image)
mineral box 713, stone 1 (of 4)
corundum var. ruby
location: Mason Mountain Mine, Franklin N.C. USA
mass: 0.65 g
(click to see larger image)
The railroad track fluoresence peaks show up at exactly the same wavelengths in all the ruby spectra. Closeup of fluorescence peaks from the first ruby's spectrum:
The spectrum from the second ruby still has a lot of statistical noise in the blue region, but there is good evidence for two absorption dips, one centered at 456 nm and deeper one centered at 443 nm (e.g., dips on either side of the 450 nm mark). The first ruby shows absolutely no evidence of absorption dips in the blue. The third ruby shows a hint of absorption dips at the two blue wavelengths.
Last edited by Brian on Tue May 08, 2007 3:49 pm, edited 3 times in total.
With the addition of the third ruby spectrum in the previous post, I thought it was looking a bit long. So I separated out the fluorescence experiment, described below:
I did another quick experiment with the first ruby, putting a red filter between the light source and stone. The red filter sharply cuts off all light below 600 nm; I was surprised at what a good job it did, since it was just a cheapie film. Here is the resulting spectrum (not normalized to incident light, since there is no green or blue light):
With the filter in place, the broad structure in the red persists, and yet the railroad track peaks (and some structure seen in the IR above 700 nm) vanish... clear evidence that these peaks arise due to fluorescence. Not that there would be much doubt, given the "crossed-filters" experiment. But this is a nice additional demonstration that only these two peaks (as opposed to the entire broad structure in the red) are responsible for a ruby's fluorescence.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
I can't think of anything that could be more rewarding than spending several hours a day glued to (I mean enthralled, inspired and enchanted by) the GemologyOnline.com forum.
Actually, the props are meant to be interpretive. This is my first attempt at Still Life art photography. That photo is entitled, "21st Century Social Engagement."
Users browsing this forum: No registered users and 7 guests
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot post attachments in this forum