Spinel is a good candidate for the title of “History’s Most Underappreciated Gem.” Some ancient mines that supplied gems for royal courts from Rome to China produced spinel, but it was usually ...

Sally Eaton-Magaña, Christopher M. Breeding, and James E. Shigley ...

We present an algorithm for enumerating all possible faceting arrangements of dihedrally symmetric diamond cuts. We first separate the question into enumerating crowns a ...

Carbonado diamond is found only in Brazil and the Central African Republic. These unusual diamond aggregates are strongly bonded and porous, with melt-like glassy patinas unlike any conventional ...

Basic, intermediate, and alkaline igneous rocks can sometimes also display similar pegmatitic textures. They include pegmatitic gabbro, syenite, and nepheline syenite, all of which are composed of ...

Figure 1. These examples of gem minerals that formed in magmatic environments are part of GIA’s Eduard Gübelin Collection. From top to bottom and left to right: 29.96 ct sanidine feldspar from Germany ...

Early diamond hunters in South Africa cared little about absolute age because diamonds were found as alluvial material in riverbeds and beaches, and only where they could be found mattered. Once ...

Prior to the discovery of kimberlites, diamonds were all mined from secondary alluvial sources: river environments where diamonds had been eroded from their primary source. Historical diamonds from ...

Such was the setting for the arrival of Art Deco – a style that celebrated the machine age. Sleek ocean liners, streamlined trains, and towering skyscrapers were favorite images to express this: they ...

Deposits of iolite (gem-quality cordierite) occur in magnesium- and aluminum-rich metamorphic rocks formed at amphibolite to granulite facies conditions. Many iolite occurrences are found around the ...

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

Diamonds have been mined in Guyana for more than 130 years and are traded in major diamond centers in Belgium, Israel, and the United Arab Emirates. Notwithstanding this long history, the primary ...