First of all to make things clear whether a red or green or blue stone, you don’t need a special Ruby filter or Emerald filter the Chelsea filter works fine for any stone also finding glass filled blue sapphires.
Anyhow back to the actual point of my discussion, I guess it has to do with the high chromium content in natural pink sapphires from Sri Lanka, no matter whether heated or unheated, pink sapphires all glow very strong red under Chelsea filter and most if not all spinels will show no reaction. Does anyone else experiencing similar results?