Saltwater Pearls from the Pre- to Early Columbian Era: A Gemological and Radiocarbon Dating Study
Examines 85 saltwater natural pearls, reportedly harvested from the Caribbean islands off the coast of Venezuela during the early 16th century, to determine their age.
Brazilian Diamonds: A Historical and Recent Perspective
Recounts the history, geology, and notable localities of diamond mining in Brazil, and outlines plans for future diamond production.
The Grand Sapphire of Louis XIV and The Ruspoli Sapphire: Historical and Gemological Discoveries
Archival research and gemological characterization reveal the true story of this 135.74 ct blue sapphire from the French crown jewels.
The Wittelsbach Blue
This article describes what is known about the Wittelsbach Blue since it was first reported in 1666, and the gemological information released to date on this diamond.
Cutting Diffraction Gratings to Improve Dispersion (“Fire”) in Diamonds
A new microlithography process developed to create high-resolution diffraction grating patterns on portions of certain facets can improve the dispersion of light and thus the amount of “fire” in a diamond.
The Challenges of Cutting a Large Gem Opal Rough
A first-person account of cutting a 3,019 ct piece of white opal to create a 1,040 ct gem with play-of-color across the surface.
A Foundation for Grading the Overall Cut Quality of Round Brilliant Cut Diamonds
The GIA diamond cut grading system described here includes the components of brightness, fire, scintillation, polish, and symmetry, as well as weight and durability concerns, into a single overall grade for cut quality for standard round brilliants.
Ruby and Sapphire Production and Distribution: A Quarter Century of Change
During the past 25 years, the corundum market has been transformed from one of medium to high-priced gems to one that encompasses nearly all price ranges.
Characterizing Natural-Color Type IIB Blue Diamonds
More than 400 blue diamonds were studied at the GIA Gem Trade Laboratory over several years to reveal additional information about the relationships between their color, clarity, and other gemological properties.
Color Grading “D-to-Z” Diamonds at the GIA Laboratory
This article discusses the history and ongoing development of GIA's color grading system, and explains how its laboratory applies it.