PGTL uses the latest equipment to ensure accurate grading, testing, and certification of diamonds and coloured gemstones.
Fourier transform infrared spectroscopy (FTIR)
FTIR (Fourier Transform Infrared Spectrometer) is a vital tool in any modern gemological laboratory. An FTIR is used for testing some of the most important gems including diamonds, emeralds, corundum, alexandrite, jade, amethyst, amber and turquoise.
FTIR is particularly important in spotting adulterated gemstones. Some treatments cannot be detected when viewed with a microscope, while FTIR can give a conclusive result.
Fourier transform spectroscopy is a less intuitive way to obtain the spectra. Rather than shining a monochromatic beam of light at the stone, FTIR shines a beam containing many frequencies of light at once, measuring how much of the beam is absorbed by the sample. Next, the beam is modified to contain a different combination of frequencies, giving a second data point. This process is repeated many times. Afterwards, the computer takes this data and works backwards to determine what the absorption is at each wavelength.
Uses of FTIR Spectroscopy include:
- 1. Distinguishing between natural & synthetic (lab grown) diamonds
- 2. Detection of sapphires and ruby corundums have been heat treated
- 3. Distinguishing between diamonds and it’s imitations such as cubic zirconia, etc
- 4. Determining zircon state in metamict or crystalline minerals
- 5. Discovering if an emerald is natural, treated, or synthetic
- 6. Distinguishing between natural and synthetic citrine
- 7. Determining if jade is polymer coated or uncoated.
- 8. Distinguishing between taaffeite, serendibite and sapphirine.
- 9. Distinguishing between scapolite and quartz
And much more. If you are looking for a gemstone testing, then precious gem testing lab in Sri Lanka or India can make sure we use FTIR spectroscopy testing
Raman spectroscopy is used to identify unknown materials.
As early as the beginning of the 2000s, Raman Spectroscopy has become standard procedure in reputable labs. Raman spectrometry is used to identify gem materials, inclusions and even fillers in a non destructive manner. Raman spectra can also be obtained on mounted gems, thus the technique plays a large role in accurately testing gems which are mounted on jewellery. It also plays a vital role in detecting a wide array of materials such as HPHT treated diamonds, treated jade, and more.
Using raman spectroscopy, gemologists can identify unknown materials from their unique Raman spectral fingerprints and compare these with known libraries of spectra.
Ideally, Raman instrumentation is used with high spectral resolution across the whole Raman range. This can identify, differentiate and investigate a wider range of materials.
Differentiation of materials
Gemologists determine if materials are the same or different by comparing their spectra. A high spectral resolution system, such as a Raman Spectrometer, enables us to distinguish even very similar crystal forms (polymorphic) of the same chemical.
Some of the uses of Raman Spectroscopy include:
1. Distinguishing between a diamond and it’s imitations
2. Distinguishing between amethyst and iolite
3. Determination of enstatite
4. Distinguishing between grossular and spessartite garnet varieties
5. Distinguishing between polymer coated or uncoated jade
6. Identification of zircon in its metamict state or crystalline state
And much more. If you are looking for a gemstone testing, then precious gem testing lab in Sri Lanka or India make sure we use Raman spectroscopy testing.
(UV-Vis or UV/Vis) refers to the absorption or reflectance spectroscopy of the ultraviolet-visible spectral region. This technique uses light in the visible and adjacent (near-UV and near-infrared [NIR]) ranges. The absorption or reflectance of the visible range directly affects the perceived colour of the chemicals involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions. This technique is complementary to fluorescence spectroscopy, in that fluorescence deals with transitions from the excited state to the ground state, whereas absorption measures transitions from the ground state to the excited state. Together, the two methods are used to accurately grade and determine the perceived colour of diamonds and other coloured gemstones, cobalt presence in spinels, and more.
The visible absorption spectra are a direct representation of the constituents (impurities, etc) that cause colour and this property is used to come to reliable conclusions. UV / VIS spectroscopy plays an important role in the distinguishing varieties of spinels, to find out if they are cobalt spinel, iron spinel or chromium component spinel from its spectra. This technique also helps in finding out the state of sapphire corundums in metamorphic or magmatic states, and much more.