Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
Hi Everyone,
I'm trying to come up with a really small and portable means of using a spectroscope at gem shows. The arrangement I presently have in mind involves a small LED pocket keychain light. But I'm not sure of the spectral components of that kind of light. I seem to be picking up a rather prominent absorption band in the blue but I'm not really sure. It's one of those "I think I see it sometimes" deals.
Can anyone else compare observations with me? I've been looking at what I think is malaia garnet with it and I'm finding manganese bands in the blue where they should be. But are they from the stone or the LED?
Rom and all,
I received a small white light LED clip-on booklight for Christmas. After checking with the spectroscope, I can verify your observations.
There was strong absorption in the lower end of the blue right into the green with weaker adjacent absorption in the blue that was hard to determine if it was a band or a series of lines. The blue area was rather broad and narrow in the violet.
I would a carefully check any light source you are considering using for spectroscopy for any type of emission or absorbtion lines.
Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
JB wrote:
Rom and all, I received a small white light LED clip-on booklight for Christmas. After checking with the spectroscope, I can verify your observations. There was strong absorption in the lower end of the blue right into the green with weaker adjacent absorption in the blue that was hard to determine if it was a band or a series of lines. The blue area was rather broad and narrow in the violet.
Thanks for the input JB. Since I posted I've been able to confirm the same thing and have adopted a filament light strategy.
Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
JB and Everyone,
There's a very interesting article by Bear Williams about ultraviolet/led lights in the current "Gem Market News." It discusses how many UV lights available today may give misleading or inaccurate results in gem ID and how led technology may provide better answers. It also provides graphs showing how various led lights perform spectroscopically.
I found the article very interesting and thought-provoking but my faith was shaken a little when Williams mentioned "malaya" and tsavorite garnets as "species." Oh well, you can't expect perfection!
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