Articles

How does one go about choosing a good gem testing lab? The gemologists at Lotus Gemology provide the following guide to help customers make the best decisions when choosing a good gem testing lab.

To the jeweler, spinel is famous for its vivid colors. But for the gemologist, this gem is unlike any other. Its extreme hardness allows a fine polish. Couple this with single refraction, which eliminates the image blurring found in most other gems, and a varied landscape of inclusion subjects, and the result is an unparalleled canvas of delight for the photomicrographic artist.

Madagascar has become one of the world’s top sources of fine blue sapphire in recent times. In addition to beautiful untreated material, increasing numbers of treated stones have appeared in the market. Some have been heated to relatively low temperatures, below 1350°C, to lighten their color. To help separate unheated and heated Madagascar sapphire, the authors performed experiments to document the changes they undergo with low-temperature heat treatment in air, which is an oxidizing atmosphere.

Short-wave fluorescent illumination provides a useful tool to spot curved banding in flame-fusion synthetic sapphire.

27 February 2019: Sapphires heated with high temperatures and low pressures (~1kbar) first entered the market in 2009, becoming more common since 2016. This article examines the process in detail and looks at the question of whether a separate disclosure is needed for the treatment.

A Burmese sapphire shows a celestial scene both externally and internally.

A look into the world of spinel inclusions that goes beyond simple octahedral crystals.

Surface-reaching growth tubes in a sapphire provide insight into the gem’s origin and treatment history.

An included calcite crystal within an unheated Burmese ruby displays dramatic twinning planes.

At the Lotus Gemology laboratory in Bangkok, we often get parcels of relatively uniform stones. But sometimes it is in this routine testing that we uncover surprises.