Description
CGL lab received in 2021/22 larger quantities of loose and mounted Lab Grown Diamonds for testing, grading, and appraising, but also rare natural-coloured diamonds, gems and imitations.
CASE 1: How to Avoid $50,000 mistake in ID of 4ct diamond, Natural / Lab-grown? 4ct SI1, K colour with unusual green fluorescence and both iD100 and EXA “refer” it?
CASE 2: a challenge to test and grade 100 lab-grown diamonds in 1 day? Combination of polariscope placed on microscope, PL inspector and EXA instruments could test stone in 5 min.
CASE 3: 100ct ‘black natural diamond” with unusually “mirror -like” surface? Certified by a “Swiss lab as Natural Black Diamond”. Simple SG/scratch tests reveal that it is black moissanite!
CASE 4: Rare type IIb diamond with unusual bluish Green-Gray colour? 0.71ct diamond from old collection for origin, clean (IF) and with ‘tatami pattern’ under Cross Polarized Filters.
GEM CASES: Surprises in testing gems that look like Yellow Sapphire, Spinel and Jade? Very rare “mint” colour emerald that is not oiled, 25-30ct oiled and resin-filled emeralds, 8ct Plus IF Intense yellow diamond, and more!
Branko Deljanin, B.Sc. FGA, GG, DGA is President and Head Gemologist at CGL Canadian Gemlab and Director of Gemmological Research Industries (Canada). Since 1999 when he detected first coloured HPHT enhanced diamonds on the market, he has spent a great deal of time studying HPHT treatments of natural diamonds and ID of synthetic diamonds (HPHT and CVD), and natural pink diamonds. In 2001 he earned his Advanced Gemology Diploma (DUG) from the University of Nantes in France, on the subject “Identification of HPHT treated diamonds”. Deljanin is an instructor of advanced gemology programs on diamonds and gems offered at workshops in 17 countries and via on-line practical seminars and webinars.
