Advanced Testing Tools
With the increasing sophistication of gem treatments and synthetics it is often impossible to positively identify the true nature of some gems with standard gemological testing instruments.
Instruments which were once exclusively used in mineralogy, chemistry and physics are now commonly employed gemologically. The caveat with this instrumentation is that it is prohibitively expensive and therefore, only affordable for major labs.
Following is a list and description of Advanced Testing Instrumentation
- 1 Spectrometry
- 2 X-ray Imaging Techniques
Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry (LA-ICP-MS)
Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) is a technique for chemical micro-analysis of solid materials. It has a wide range of applications in many different fields of science and industry. It identifies elements based on their atomic mass. A small sample of the material is vaporized by a laser, ionized and sent into a mass spectrometer which identifies each element.
Standard testing of gemstones by LA-ICPMS involves destroying very small quantities of the material being tested. The laser beam produce a small pit, measuring approximately 50 micrometers in diameter (half the diameter of a human hair). Typically four samples are taken from the girdle of a gem. The weight loss from these pits is negligible.
Gemological Uses for LA-ICPMS:
- determine beryllium-treatment of corundum
- identifying 'Paraiba"-type copper bearing tourmaline from Brazil, Nigeria and Mozambique
- origin determination of emeralds and other minerals containing unique elements specific to a locality
- Separation of Natural and Synthetic Amethyst and Citrine
This technique is the the modern, mechanized equivalent of using a diffraction grating or prism spectroscope,with the main difference being that the spectrum is displayed on a screen as a continuous graph, which represents the intensity of the absorption, as opposed to bands within a rainbow. A UV-Vis-NIR spectrometer covers a much broader range than a standard hand-held spectroscope.
UV-Vis-NIR: 190-1100nm and can be extended to 3000nm
Standard Spectroscope: 400-700nm
Two types of spectrometers are generally used:
- scanning spectrometers, which only measure absorption
- diode spectrometers,which measures both absorption and emission
Gemological Uses for UV-Vis-NIR Spectroscopy:
- Detection of GE POL high-pressure high-temperature (HPHT) annealed nominally type IIa diamondsUV-Vis-NIR Spectroscopy
- Analyzing trace elements to identify the geographical origin of gems
- Detecting gems that have undergone heat treatment to alter their appearance
Energy Dispersive X-ray Fluorescence (EDXRF)
Laser Induced Breakdown Spectroscopy (LIBS)