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. In the absence of inclusions or ...

Observations of Oval-, Pear-, and Marquise-Shaped Diamonds: Implications for Fancy Cut Grading Presents findings from observations of oval-, pear-, and marquise-shaped diamonds, laying the groundwork ...

GIA’s laboratories use advanced instrumentation and research to deliver accurate grading, identification, and origin ...

This large Australian light opal cabochon weighs 117.85 carats. Small play-of-color flashes of orange and green predominate in a pinfire pattern, with spots of a more muted blue over a grayish ...

GIA will offer convenient access for colored stone identification and identification and origin laboratory services at the show. Drop off your stones for expert analysis and report services in the ...

Criteria for distinguishing emerald filling substances were investigated. Thirty-nine fillers were divided into six substance categories—three “presumed natural” (essential oils [including cedarwood ...

One of the most famous gems in the world, The Hope Diamond is a 45.52 carat Fancy Deep grayish blue diamond. GIA researchers examined it in 1988. Photo: Chip Clark, courtesy of Smithsonian Institution ...

Harness the power of knowledge with the industry-leading instruments that GIA uses in its grading laboratories. Representing more than 85 years of research and the combined expertise of GIA’s ...

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 ...

Pink-to-red coral has a long history as an ornamental gem material in jewelry, carvings, and sculptures. However, due to a variety of environmental and legal factors, the supply of high-quality, ...

The separation of naturally colored lavender jadeite from color-treated material is a problem that has long plagued gemologists. One theory is that the dyeing agents being used are of an organic ...

A potential new synthetic gem material in the form of a faceted 0.88 ct brownish yellow nano-polycrystalline diamond (NPD) has undergone a full gemological examination, including detailed ...