Latest GRS News


Retake of GRS presentation on HPHT-treated sapphires from 2019 GILC meeting in Tucson, AZ

One of the topics discussed at this year’s GILC meeting in Tucson, AZ (held on 4th February 2019) was “Pressure /Temperature Corundum Treatment”. GRS had been invited in order to present our findings on the topic. Mr. Edward Cleveland, research staff at GRS in Bangkok, represented GRS at the event and gave a presentation called “HPHT (PHT) […]


Q&A on PHT-treated sapphires published in Southern Jewelry News

Sapphire, as well as most colored gemstones today are routinely treated to improve their appearance and increase their salability. Simple heat application, often called ‘cooking’ is an ancient method of enhancing colored stones. Depending on the stone itself, other forms of enhancement may be applied. Diffusion heats sapphires at a high temperature and adds certain […]


New types of synthetic periclase identified by C2S inclusions – dicalcium silicate cement hardener

Naturally occurring periclase is a relatively common mineral phase. Due to its small crystal sizes, it never gained recognition in the gem-industry in terms of commercial importance. Synthetic periclase is commonly used for technological applications and is available in large quantities and sizes (Joachin et al., 2012). In the past, synthetic periclase was marketed in […]

Alerts, News

AGTA announces guideline of full disclosure for pressure and heat-treated sapphires

AGTA announces guideline of full disclosure for pressure and heat-treated sapphires (GRS type “PHT” or HPHT). GRS welcomes this decision. AGL and then AGTA have also adapted GRS’ position of full transparency which stands in sharp contrast to the recent decision made by LMHC (Laboratory Manual Harmonization Committee). LMHC has decided not to distinguish or […]


Identification and characteristics of PHT (‘HPHT’) – treated sapphires – An update of the GRS research progress (update 12 November 2018)

A series of peculiar events that commenced in 2015 brought a degree of uncertainty to the Sri Lankan gemstone industry. Sri Lanka is known as the world’s foremost producer of ‘heated’ corundum. So far only corundum of higher clarity has been used to produce clean sapphires. It was noticed that a few buyers began purchasing […]


Spinel formation by sulphur-rich saline brines from Mansin (Mogok area, Myanmar)

During the last 2 decades, one of the authors has mapped the mineral occurrences in the Mogok valley and registered the mineral assemblages of approximately 100 spinel mines in a profile of 30 km length (first part published in Peretti et al., 2007 and Peretti & Tun 2016). Abstract from 15th Swiss Geoscience Meeting, Davos […]


The Perettiite Space Odyssey

A compilation of footage of the rare and complex silicate–borate mineral Perettiite-(Y). It was first discovered in 2015 by Dr. A. Peretti as an inclusions in a phenakite crystal from Mogok, Myanmar.


Warning: Synthetic Padparadscha sold as Natural in the trade.

During testing at GRS we have encountered an orangy-pink sapphire reminiscent of heated padparadscha. An 8.60 ct example was identified as synthetic during high-tech testing, identified as containing Cr and Ni concentrations, and a broad infrared band around 3000 cm-1. Although the customer was informed of the stone being synthetic, it might be possible that […]

Alerts, News

Updated terminology for HPHT-treated sapphires

Meggen, 7 September 2018 GRS has decided to update the treatment disclosure terminology used for sapphires enhanced by heat at elevated pressure (published in the literature as HPHT, Song, J. et al. 2015) Generally the pressure applied to diamonds during the diamond HPHT treatment process is much higher than that of the sapphire treatment. GRS […]

News, Uncategorized

Retake of GRS presentation from 2018 GILC meeting in Tucson, AZ

Due to numerous requests from members of the trade who were not admitted to this years GILC meeting, we have recorded a recap of the speech given by Dr. A. Peretti and made it available for the public. The topic of GRS’ presentation is “Color and Origin”, where we elaborate our approach towards the use […]