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ANALYTICAL METHODS

Traditional Analytical Methods

 

Microscope - An essential and very important aid for the observation of internal features of gemstones. The inclusions of certain minerals or gemstones are very typical for its geographical origin. Using a microscope, heat treatments or clarity enhancements can also be identified.

Refractive Index - A ratio which indicates the 'optical density' of a substance. It is related to the angles of incidence and refraction of light. The refractive index is different for most gem-species.

Specific Gravity - Specific Gravity (SG) is the ratio of the weight of a substance to the weight of an equal volume of water. Every gem has its own specific gravity and the SG can be used as an additional value in gemstone identification. Hydrostatic balance is used

Polariscope - An optical instrument used in testing transparent gemstones to distinguish between isotropic and anisotropic materials.

Dichroscope - An instrument for detecting pleochroism in a material. It is constructed that two pleochroic colours, or shades of colour, may be detected and compared side by side in a single view.

Balances - We uses several different balances (Mettler & Sartorius auto calibration carat balances). Each stones is weighed in at least 2 different balances.

 

High-Tech Analytical Methods

FTIR (Fourier Transform Infrared Spectroscopy)
Infrared spectrometers are used to measure absorption in materials within the infrared part of the electromagnetic spectrum. In infrared spectroscopy, IR radiation is passed through a sample. Some of the infrared radiation is absorbed by the sample and some of it is transmitted. The resulting spectrum represents the molecular absorption and transmission, creating a molecular fingerprint of the sample. Like a fingerprint no two unique molecular structures produce the same infrared spectrum. This makes infrared spectrometry very useful for several types of analysis. For example to:

  • Detect polymers, oils and resins used for impregnation, e.g. in jadeite, opal or emerald
  • Distinguish certain natural and synthetic gem materials, e.g. emerald
  • Opinions on heat treatment on ruby and sapphire

 

UV-VIS (Ultraviolet-Visible Spectroscopy)
UV spectrometers are used to measure and record characteristic absorption patterns within the UV radiation range of the gemstone. The UV-VIS spectrometer is used to:

  • Investigate the origins of emeralds and sapphires, where stones of certain different origins may produce different absorption characteristics in the UV and visible regions of the spectrum
  • Distinguish between natural corundum and synthetic corundum, e.g. to compare iron-rich natural rubies with iron-poor synthetic rubies