Traditional Gemmological Methods

Traditional gemmological tools and methods play an important role in determining the nature of mineral species, which mainly involve determining the physical and optical constants and comparing with tables of their standards, available in common gemmological texts. These mainly provide qualitative information but still considered as important tools for gem identification. The most commonly tools used are polariscope, dichroscope, refractometer, spectroscope, UV lamp and specific gravity measurements

Microscopy

The microscope remains the most important tool in gem identification – it is the ‘heart’ of a gemmological lab. Detailed and careful observations made under a microscope help a gemmologist to decide on many aspects of a gem regarding its type, origin, treatments, etc and assists other techniques in validating the data. At the IIGJ-RLC, every analysis is started with a detailed microscopic observation.

Fourier Transform Infrared (FTIR) Spectrometer

Due to a typical crystal structure with specific pattern of molecular arrangement, particular gemstones or minerals tend to produce a characteristic absorption and transmission patterns on interaction with light. FTIR typically uses infra red light to study such features.

At IIGJ-RLC, FTIR is commonly used to identify unknown gems and minerals by their fingerprint pattern, separate natural and synthetic emeralds, rubies, sapphires, amethysts, etc, determine absence or presence of treatments in rubies, sapphires, emeralds, turquoise, corals, etc.

Ultra Violet-Visible - Near Infrared Spectrometer

UV-Vis-NIR spectrometry is based on selective filtering of wavelengths through the sample; the absorbed wavelengths caused due to electron defects or chromophoric elements are displayed in the form of a graph and expressed in comparison with the incident light.

At IIGJ-RLC, UV-Vis-NIR spectrometer is used to identify a gem species / variety, especially in case of separation of emerald from green beryl or ‘cuprian’ tourmaline from ‘non-cuprian’, or the type of garnet; it also helps to differentiate synthetic from natural sapphires or spinels, turquoise or corals their imitations, etc; it is also very useful in separating treated corals, jadeites, turquoise, diamonds, etc.

Ultraviolet Imaging - DiamondView™

DiamondView™ basically is an imaging system, which uses the short-wave ultraviolet light below ~225 nm. The fluorescent reactions are observed through a CCD camera, which display them on the monitor through software. It helps in studying the growth pattern of the sample’s surface or sub-surface up to few microns. It also assists in observing 'phosphorescence' of a sample.

Although, DiamondView™ was created to study and separate synthetic from natural diamonds, it has proved to be quite useful for identifying treated and synthetic counterparts of rubies, sapphires, emeralds, etc.

SynthDetect™

Another screening equipment developed by DeBeers Group Industry Services for separation of natural and synthetic (lab-grown) diamonds. At IIGJ-RLC, this screening instrument is used to screen diamonds mounted in jewellery before they are graded. In addition to mounted diamonds, SynthDetect™ is also used to screen packets of polki-cut loose diamonds. 

Diamond Cut Scanner

The scanner basically measures dimensions of cut & polished diamond and gemstones, where it scans angles of inclination and position of each facet and measures each facet edge to create a 3D wireframe model. The software calculates exact proportions and symmetry of a cut diamond, thereby providing information on the performance of light within a cut diamond.