DGL (Delhi Gemological Laboratories), New Delhi, India, observed a mind distracting figure of as high as 26.5% diamonds received as fracture-filled (treated) diamonds in the lab last year.
What is Fracture filling?
Fracture filling is a process during which a glassy material such as lead glass, which has high refractive index, fills the surface breaking feathers (locally in trade called as cracks/ JHIRAM). If such material penetrates the cracks they become practically less visible, because with the filled material having high refractive index, the light refracts at a similar speed and the stone looks much cleaner than before. Generally, this treatment is done on bigger stones due to the cost factor. But we have received such treated / Fracture filled diamonds of size as small as 0.075 carats. Star sizes are also observed to be treated. That is a very common size used in jewellery. Such treated (fracture filled) diamonds are not clarity graded.
Advantages of Fracture filling?
Since such material penetrates the cracks, the feathers become practically less visible. Such diamonds fetch better price in comparison to the price before doing such treatment by quoting it at a higher grade or they are mixed with a similar looking grade packet of melee or higher size pointers.
It has been observed that this material is also used to fill laser drill treated diamonds.(see picture)
Disadvantages of Fracture filling?
Unfortunately the treatment is not a permanent change since slight heating of the stone during repairs of the jewellery piece can make this filled material darker and the cracks become quite visible. But the treatment is considered much better than the regular oil filling. That is why such method is also popular with emerald and other precious stones.
1) Under magnification, the cracks appear to be completely filled, except near the surface, which appears like a thin scratch on the surface. Sometimes the filled material also shows some hazy or cloudy appearance. Occasionally, this filled material also shows flow texture.
2) Another effect shown by this material is known as flash effect. The typical flash effect shown by the material is violet-blue in bright field illumination and yellow to reddish-orange in dark field. (see picture)
3) Gas bubbles are also noticed which were distributed evenly throughout the filling.
It is recommended that diamonds identified with filled material should be removed from the setting before doing any repair work.
While sorting diamond packets, a blue or a bluish reflection indicates flash effect of fracture filling. Mark them separately.
The price range for any size is approximately 25% to 55% cheaper than the non treated diamonds of similar looking grade.
Such treatments are not easily identified by Diamond traders/ jewelers unless they are aware or they have learnt about the same.
People in trade selling such goods name it in a sophisticated term as Clarity Enhanced.
The analysis was done by:
DIP. Gemmology (I.G.I.),
GIA Diamond Graduate,
Advance Gemology (GIA)
Pearl Grading (GIA),
G.R.S.S (World Gold Council)
Gold Appraiser (Ministry of M.S.M.E., Govt. Of India)
Chief Gemologist | Head of Department
Harison Delhi Gem and Jewellery Institute,
|- By Mr. Ashish Kalra|