Cuprian (copper-bearing) tourmaline, known as “Paraíba” tourmaline in the trade, has been an important gem since its discovery in 1989. Until now, almost all of the material reported has been ...

Earth’s surface is divided into tectonic plates, and the ones that make up the ocean floor are destined to sink. Sheets of oceanic crust typically bend and sink down into Earth’s interior at so-called ...

Insight into amethyst mining activity in Morocco. Characteristic “hourglass” color zoning (figure 1) and striking red hematite “finger” inclusions help distinguish Moroccan amethyst. Although amethyst ...

Intriguing Sapphire from Montana, a New Source of Emerald in Central China, and Arkansas Turquoise Duncan Pay, Editor-in-Chief Reports on a new source of primary gem-quality sapphire from Montana, ...

The following guide will give a short description of the treatment process, some gems for which the process is used, how easy or difficult the treatment is to detect for a trained gemologist, how ...

Yusuke Katsurada, Ziyin Sun, Christopher M. Breeding, and Barbara L. Dutrow ...

When the same gems and precious metals are used in jewelry, design is the element that ultimately distinguishes one piece from another. Real success is measured not only by the value of its materials ...

Gem and mineral hardness is measured on the Mohs scale. The numbers are based on the relative ease or difficulty with which one mineral can be scratched by another. But the Mohs scale is deceptive.

Emerald is 7.5 to 8 on the Mohs scale and has fair to good toughness, making it a stone that requires more care in wearing than ruby or sapphire. Even so, emeralds are beautiful stones for all types ...

Like the white opal, the black opal is found at the contact zone between the volcanic rock series and the underlying clay-rich layer (figure 2). The layer is one in a sequence of repeating volcanic ...

Opal hardness is variable depending on its exact composition and formation conditions, and ranges from 5 to 6.5 on the Mohs scale. Its toughness is very poor to fair, making opal a gem that is ...

Gem and mineral hardness is measured on the Mohs scale. The numbers are based on the relative ease or difficulty with which one mineral can be scratched by another. But the Mohs scale is deceptive.