just got this in email, and it looked like it might be of general interst - using Raman spectroscopy for gem ID
Gem Identification Using Portable Raman
In our new video, Dr. Henry Hänni, Professor Emeritus of Gemmology and retired Director of the SSEF Swiss Gemmological Institute in Basel, Switzerland, discusses the advantages of the GemRam® portable Raman spectrometer for gem identification and verification. Dr. Hänni’s comprehensive gemstone collection, featuring gemstones from all over the world, was used in creating the GemID® software, which is utilized with the GemRam for fast and reliable gemstone identification results.
Joined: Fri May 12, 2006 11:24 am Posts: 7523 Location: Rome, Italy
Cool Video, as usual Prof. Hanni explanation is direct, easy to understand and exhaustive. The only thing he didn't mention (or maybe i didn't hear it) is, Identification means it is no or VERY rarely possible to discriminate natural from synthetic material. The GemRam is an IR laser based Raman system. It is indeed very effective for material identification and IR reduces the possibility of luminescence effect in materials so, the identification in the fingerprint area is almost always possible. BUT. On the other hand, the luminescence noise effect can be turned into an advantage and this is what a Visible laser based Raman system does. It works, in this way, as a Photoluminescence (often abbreviated as PL) spectroscopy system, so you basically have 2 different spectroscopy techniques available with one instrument only. PL Spectroscopy is a relatively “young” technique when it comes to Gemological applications but is the one which is giving the best results in many of our very specific fields In diamonds, lattice defects of VERY minor extent can be easily resolved by PL spectroscopy. I am talking about defects so small that are in many cases below the sensitivity of FTIR spectroscopy. Practically ALL the studies involving the most recent diamond treatments and synthetics are based on PL spectroscopy as main technique. Many chemical elements we are all familiar with have their distinct PL reaction which in many cases is diagnostic about the nature of the material (schist, non schist, synthetic emeralds as an example). The list of possibilities is long and…….as studies going on, growing. So , at the end of the day it would be very cool to have a Raman system provided by multiple wavelengths capability (IR and visible) but those units are REALLY expensive and not exactly affordable for the average gemologist. Then, if I would be on the market for a Raman system, I likely would choose one which gives me the more information possible about what I am testing. Of course any choice is respectable, although, sometimes not easily to understand. Sidenote: the GemRam system is based on a Raman probe which may be very handy in some cases but, well, it is actually pretty delicate. Call it portable is of course the truth since the unit seems compact but I would be very careful …..
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