Reference material for the working gem trade.
Written by practising gemmologists, laboratory analysts and trade-compliance specialists. Free to read.
Identifying heat treatment in Ceylon sapphires
The commercial gulf between unheated and heat-treated corundum has widened significantly over the last decade. A working guide to the diagnostic features a trade buyer should be able to read.
Dr. Ranil Perera, FGA · 9 min read · March 2026
The Ratnapura alluvial basin: a geological ledger
The secondary deposits of the Ratnapura district have produced sapphire, ruby, spinel, cat's eye and alexandrite continuously since the classical period. A short account of why the ground is so productive.
12 min read · February 2026
Reading inclusions: what silk, feathers and crystals tell you
A gemstone's inclusion scene is its passport. What to look for under 10x and 30x when a laboratory report is not available.
8 min read · January 2026
Reading gemmological certificates: NGJA, SSEF, Gübelin and GRS
Not all laboratory reports carry the same weight in the international market. A short guide to which certificate matters for which purpose.
7 min read · December 2025
Alexandrite and the physics of colour change
Sri Lanka is the world's second most significant source of alexandrite. Why the stone changes colour, and what to look for when the change is real.
6 min read · November 2025
Sri Lankan gem export compliance: a practical primer
Every stone leaving Sri Lanka passes through the NGJA. A short guide to how the process works, what documentation is required, and where buyers most often trip up.
10 min read · October 2025