DiamondView as the name suggests, was developed by the Diamond Trading Company to screen diamonds for determination of natural and synthetic origin. The instrument basically is an imaging system, which uses the short-wave ultraviolet light below ~225 nm. The sample is targeted with the ultraviolet light and fluorescent reactions are observed through a CCD camera, which captures the fluorescent reactions and display them on the monitor through software. DiamondView not only assists in observing the fluorescence of the sample, but also its growth pattern as the CCD camera magnifies the sample, enabling to view the structure properly, against a gemmological ultraviolet lamp. The fluorescence image produced is of the surface or sub-surface up to few microns. It also assists in observing 'phosphorescence' of a sample.
The fluorescent reactions not only indicate the presence of impurities but also the conditions in which a gem has formed. Therefore, the fluorescence in many gems such as diamond, ruby or sapphire follows the growth pattern or crystal structure, and this helps to differentiate between natural and synthetic counterparts, and in some cases, treated.
Schematic principle of DiamondView
The growth patterns of natural and synthetic gems are not exactly the same, and have different concentration of impurities; the pattern of fluorescence also differs and assists in their separation. Same applies to treated counterparts, where original impurities are either modified or additional impurities are introduced in the structure; in both cases, the pattern of fluorescence changes. Colour of the fluorescence, spacing between the growth bands, complexity and visibility of the pattern will vary in natural stones whereas in synthetic stones the patterns are very much uniform due to consistency in growth rate.
At the Gem Testing Laboratory, DiamondView is used to:
Separate natural stones from synthetic counterparts, as in case of diamonds, for which this instrument was specifically developed; however, this has proved to be very useful for other gems too in studying and understanding their structures, such as rubies and sapphires.
Growth patterns in natural diamond following octahedral as well as cubic faces may be seen in cut samples in the form of squares (right) and triangles (left), along with blue fluorescent colours.
HPHT-Grown synthetic diamond displaying the central cubic core with arms emanating from four corners, associated with the dodecahedral faces (left). Such pattern forms an 'hour-glass' effect. The green fluorescence is also associated with a synthetic HPHT grown type I diamond. While a CVD diamond (right) displays a characteristic layered / banded fluorescence.
Natural sapphire showing angular growth zones (left), while synthetic flame-fusion corundum displays curved banding (centre and right). Such features which are difficult to observe in light coloured corundum under a gemmological microscope become quite clear with DiamondView imaging.
To identify treatments, such as fracture fillings in diamond, ruby or emerald, coating and dyeing on various gems, use of coloured oils 'joban' in rubies or sapphires, diffusion in natural or synthetic corundum, heating in rubies or sapphires, etc.
Glass filled fractures (blue areas) in ruby stands out very clearly against a red fluorescence of ruby (left). Glass filled fractures in diamonds (centre) and resin-filled fractures in emerald (right) also show the unevenness of filling, by their patchy fluorescent reactions.
Coloured oil 'joban' in fractures of a ruby bead (left) display bright orange-yellow fluorescence, assisting not only in detecting the filler but also the position of fractures. While coloured coatings in colourless beryl (centre) and ruby (right), can be detected by unusual surface fluorescence, not associated with natural counterparts. Also note the dark, non-fluorescent facet edges, caused due to chipping of coated substance, revealing their base material.
An unheated natural blue sapphire displaying fine straight zones with orange red fluorescence (left), while heat-treated sapphires(centre and right,) show strong chalky blue / greenish / white fluorescence, following the growth zones, with or without orange-red background fluorescence.