This 6.30-carat black boulder opal from Queensland, Australia, displays vivid play-of-color. Black opals are highly valued because their dark body tone showcases play-of-color more dramatically than ...

The fee for the GIA Laboratory-Grown Diamond Quality Assessment is US$15 per carat, with a minimum fee of $15. Submissions that do not meet the minimum criteria for assessment will be charged a US$5 ...

Explore sapphire history, research, quality factors, and more in the GIA Gem Encyclopedia.

CARLSBAD, Calif. – June 2, 2025 – Beginning later this year, GIA (the Gemological Institute of America) will start using descriptive terms to characterize the quality of laboratory-grown diamonds and ...

Once a stone is submitted, client information is withheld from the non-client-facing staff who conduct the analysis. This measure helps ensure an unbiased report. Before undergoing examination, each ...

Industry analysts project that by 2025, 20% of all diamonds on the market will be laboratory-grown. Indeed, the gem industry has seen a significant increase in the quantity, size, and quality of ...

Explore diamond history, research, quality factors, and more in the GIA Gem Encyclopedia.

At the earth’s surface, graphite is the stable crystalline form of carbon, with a density of 2.26 g/cm 3. Diamond is a much more compact form of carbon, with a density of 3.52 g/cm 3, 56% higher than ...

The change in relative abundance of the various minerals from the original rock to the final sedimentary products is a measure of their comparative resistance to weathering. In our Winter 2022 column, ...

In November 2022, a parcel of 24 approximately 0.5–1.2 ct spinel crystals, described as cobalt-diffused, were obtained directly from a treater by the research team at GIA in Bangkok. Of these, seven ...

While the study of inclusions might seem to be a modern concept requiring the use of advanced microscopes with sophisticated optical lenses, early naturalists did have some basic knowledge of how ...

Welcome to the Winter 2021 issue of Gems & Gemology! This exciting conclusion to the volume year features new content examining blue Burmese sapphires, the source of rich olive color peridot in Pyaung ...