Greenish yellow to yellowish green HPHT-treated diamonds exhibited highly saturated body color, well-defined brown to yellow octahedral graining, and visual evidence of heating, among other characteristics.

There has been considerable debate in the gem trade concerning the nucleation procedures being used to grow large round Chinese freshwater cultured pearls.

Results from spectroscopic analyses of GE POL high-pressure high-temperature (HPHT) annealed nominally type IIa diamonds are presented, and these spectral characteristics are compared with those of untreated diamonds of similar appearance and type.

Lapis lazuli has been mined from the Coquimbo Region of Chile since 1905.

Gemological, chemical, spectroscopic, and microscopic properties of blue-green color-change garnets from a new deposit near Bekily, Madagascar, are given.

Criteria for distinguishing emerald filling substances were investigated.

Greater amounts of colorless sapphire—promoted primarily as diamond substitutes, but also as natural gemstones—have been seen in the gem market during the past decade.

Over the last 10 years, millions of carats of turquoise have been enhanced by a proprietary process called the Zachery treatment.

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.

The successful culturing of abalone pearls has been known since French scientist Louis Boutan’s experimentation in the late 1890s, but commercial production has been achieved only in recent decades.

A mathematical model which can analyze how appearance factors depend on proportions.

Two ecclesiastical objects of the late Gothic period (1350–1520) were investigated to identify the gemstones that adorn them.

Natural and synthetic gem rubies can be separated on the basis of their trace-element chemistry.

This article reviews the rise of the modern diamond cutting industry in India and its impact on the world diamond trade.

Synthetic emeralds grown hydrothermally in an alkali-free, chlorine-bearing solution have been manufactured in Guilin, China, since 1987.