Inorganic Gemstones

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LRS

In recent years LRS has assumed significance as a very useful technique in gemology. The Raman microscope can be focused to observe very small inclusions and provides a quick spectral analysis in a non-destructive manner.

The LRS consists of:

  • A classical microscope
  • Laser excitation source
  • Spectrometer for detecting the scattered light energy
  • Computer for data collection and analysis Procedure

Procedure:

  • An Argon laser beam is impinged on the sample being tested.
  • A small fraction of this incident light interacts with the vibrational modes of the surface being examined.
  • The energy differences of the scattered light are detected by a spectrometer and than analysed by comparison with the database.
  • Absorption regions define the vibrational modes of the molecular groups and structural bonding thereby making it a useful tool for elemental analysis.
  • It is a quick and accurate technique.

Applications:

  • Gem Identification - unknown gem stones; Natural / synthetic identification
  • Study of inclusions and internal structure helps in:
    1. Identification of geological environment and origin of gemstone.
    2. Identification of exact nature of fracture fillers i.e. resin, oil etc.
    3. Identification of the treatment i.e. heat, irradiation etc.
    4. Identification of the enhancement by impregnation of opal, jade etc.
  • Studded Jewellery.

Disadvantages:

  • In identification of organic gemstones; fluorescence spectra of some inclusions are quite common and hence can give misleading results.

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