Largest Blue HPHT Synthetic Diamond
Analysis of a 5.03 ct HPHT-grown blue synthetic diamond, the largest ever examined by GIA.
Calcium Fluoride Coating Found on 13 "Fancy" Pink Diamonds
Recent lab examination reveals that traditional treatments such as calcium fluoride coating are still prevalent in the trade, and great care must be taken to identify them.
Turquoise with Fingerprint Pattern
A fingerprint pattern, possibly left by human skin oils during the assembly process, is observed in natural turquoise beads.
Atypical Freshwater Cultured Pearls with Damaged Nacre
The New York lab received four baroque-shaped pearls with damaged nacre layers
Diamond with Unusual Laser Manufacturing Remnant
An unusual laser manufacturing remnant, possibly once used to guide a gem cutter, was left behind in a clock-like shape.
Spring 1991 G&G Lab Notes
This section, from the Spring 1991 issue of Gems & Gemmology, is a compilation of interesting finds from GIA’s laboratories.
Very Large Rough Diamond
A report on a 1,138 ct rough diamond, possibly the largest ever examined by GIA.
A Useful Technique to Confirm the Hydrophane Nature of Opal
Observing a water drop’s interaction with opal, as well as refractive index, can confirm a specimen’s hydrophane nature with less risk of breakage than total immersion.